View as PDF

Adverse, Non-adverse and Adaptive Responses in Toxicologic Pathology

View as PDF
1. INHAND Nomenclature Non-Neoplastic – Hepatobiliary Bob Maronpot (Email: maronpot@me.com) (Website: Focusontoxpath.com) Modular Education Course: Toxicologic Pathology of the Hepatobiliary System Embassy Suites Raleigh-Durham Raleigh, North Carolina October 23–26, 2016 Paul Watkins, MD, University of North Carolina Chapel Hill Course Objective The objective of this Society of Toxicologic Pathology (STP) Modular Education course is to educate individuals in the principles of toxicologic pathology of the hepatobiliary system. Course Description The STP course will bring together course attendees and world renowned subject experts for didactic lectures and practical sessions including whole- slide digital images and data sets. The course will be held in an environment that facilitates an intensive learning experience. Practical evaluation and interpretation of toxicologic pathology data will be emphasized. Who Should Attend The STP Modular Education courses are designed with the novice toxicologic pathologist in mind; however, pathology residents/graduate students with an interest in toxicologic pathology or experienced pathologists who desire a more in-depth review in toxicologic pathology of the hepatobiliary system Course Registration (Includes lodging Sunday night to Tuesday night) Early Registration (through August 31, 2016) Registration (September 1–30, 2016) STP Member (Single lodging) $1,350 $1,500 Nonmember (Single lodging) $1,550 $1,700 Student Member* (Single lodging) $750 $800 Local Registration (Lodging not included) Early Registration (through August 31, 2016) ) Registration (September 1–30, 2016) STP Member $750 $900 Nonmember $950 $1,100 STP Modular Course Student Travel Awards The Society of Toxicologic Pathology (STP) is pleased to offer the STP Modular Course Scholarship to eligible students and trainees with demonstrated interest in the field of toxicologic pathology. This scholarship is intended to cultivate those interests by exposing trainees to in-depth applicable knowledge in subspecialties of Toxicologic Pathology, while also facilitating interactions and networking opportunities for trainees interested in pursuing a career in Toxicologic Pathology.
2. Acknowledgements •  Photomicrographs from NTP Archives •  Photomicrographs and information from the NTP Non- Neoplastic Lesion Atlas (http://ntp.niehs.nih.gov/nnl/) •  Photomicrographs from important colleagues •  Dave Malarkey •  Rick Hailey •  Jerry Ward Disclaimer Opinions expressed are mine and not necessarily in agreement with my INHAND colleagues or the NTP
3. Categorization of Hepatic Responses •  Cytoplasmic Alteration Cytologic Alteration •  Clear cell change •  Hypertrophy – Enzyme induction •  Peroxisome proliferation •  Fatty change •  Cholestasis •  Atrophy •  Infiltration/Inflammation •  Cystic Change •  Cystic degeneration •  Biliary cysts •  Vascular Effects •  Angiectasis •  Infarction •  Cell Death •  Necrosis & Apoptosis •  Proliferative Responses •  Foci, Hyperplasia •  Cholangiofibrosis
4. Hepatodiaphragmatic Nodule
5. Hepatodiaphragmatic Nodule ies gs, on- unt on nal for all or- of og- tis forms and be of different origin. They mostly occur as isolated effects and are considered by the pathologist in distinguishing background hepatic lesions versus xenobiotic-induced lesions that occur in rodent preclinical toxicity studies. Hepatodiaphragmatic Nodule (Figures 3 and 4) Pathogenesis: Developmental alteration. Diagnostic features: Visible grossly and tinctorially similar to normal hepatic parenchyma. Rounded extensions usually of the medial lobe(s). Increased mitoses, cytological alterations, and nuclear alterations may be present. Linear chromatin structures with small lateral projec- tions are pathognostic. at Society of Toxicologic Pathology on August 8, 2013
6. Hepatodiaphragmatic Nodule e m es s, n- nt n al or ll r- of g- is Developmental anomalies occasionally occur in the liver of rodents. These malformations might be expressed in different forms and be of different origin. They mostly occur as isolated effects and are considered by the pathologist in distinguishing background hepatic lesions versus xenobiotic-induced lesions that occur in rodent preclinical toxicity studies. Hepatodiaphragmatic Nodule (Figures 3 and 4) Pathogenesis: Developmental alteration. Diagnostic features: Visible grossly and tinctorially similar to normal hepatic parenchyma. Rounded extensions usually of the medial lobe(s). Increased mitoses, cytological alterations, and nuclear alterations may be present. Linear chromatin structures with small lateral projec- tions are pathognostic. Society of Toxicologic Pathology on August 8, 2013
7. Hepatodiaphragmatic Nodule This is probably pathognomonic.
8. Ectopic Pancreas
9. Subendothelial Hepatocytes
10. Subendothelial Hepatocytes
11. Subendothelial Hepatocytes female B6C3F1 mice were 3/50, 1/50, 15/50, 47/50, and 0/49, 2/ 50, 20/50, 46/50, respectively. Although there was a high inci- inflammation, pigmentation, hepatoblastomas, hepatocellular adenomas, and hepatocellular carcinomas. However, the lesion FIGURE 7.—Continued 168 ELMORE ET AL. TOXICOLOGIC PATHOLOGY Vol. 41, No. 2, 2013 2012 NTP SATELLITE SYMPOSIUM 169 170 ELMORE ET AL. TOXICOLOGIC PATHOLOGY Toxicologic Pathology 41: 151-180 (2013)
12. Amyloidosis ho- located centrally in hepatocytes that exhibit positive immuno- histochemical staining for LAMP-2 (Figure 17) but is nega- tive for Oil-Red-O and adipophilin is indicative of phospholipid accumulation (Obert et al. 2007). Amyloidosis (Figures 18 and 19) Pathogenesis: Cellular process related to misfolding of protein. Diagnostic features: Deposition of pale, homogeneous, amorphous eosi- nophilic material. Deposition often peri-sinusoidal, periportal, or involving blood vessel walls. Localization is extracellular.s. at Society of Toxicologic Pathology on August 8, 2013
13. Pigmentation 007). n a ally rada rred and alls. ften gen- nflu- Coe Liu tion pria ung, isto- ain- ight d by rmal phic s ar m Pigmentation (Pigment Deposition) (Figures 21–25) Pathogenesis: Incidental occurrence and secondary to cellular and erythryoid breakdown products; lipid peroxidation of cel- lular membranes; altered heme metabolism. Diagnostic features: Lipofuscin: Pigment can be seen in hepatocytes as well as in Kupffer cells. May vary from pale yellow to deep granular brown. May be sudanophilic with autofluorescence under ultraviolet light. Often located adjacent to bile canaliculi. Iron/hemosiderin: Can be yellow to brown. May be finely granular. Usually appears intracellularly in Kupffer cells and hepatocytes. Porphyrin: Pigment is dense dark brown to red-brown and when viewed with polarization is bright red with a centrally located dark ‘‘Maltese cross.’’ Brilliant red fluorescence when viewed in fresh frozen sections; fades with exposure to ultravio- let light. Most often located in bile ductules and bile canaliculi. Bile (cholestasis) (Figures 23–25):
14. Pigmentation
15. Mineralization Male B6C3F1 Mouse Tx: 2-Chloronitrobenzene Dx: Chronic inflammation with mineralization
16. Pigmentation – Bile Can be yellow to brown. May be finely granular. Usually appears intracellularly in Kupffer cells and hepatocytes. Porphyrin: Pigment is dense dark brown to red-brown and when viewed with polarization is bright red with a centrally located dark ‘‘Maltese cross.’’ Brilliant red fluorescence when viewed in fresh frozen sections; fades with exposure to ultravio- let light. Most often located in bile ductules and bile canaliculi. Bile (cholestasis) (Figures 23–25): Appears as elongated pale green-brown plugs within bile caniculi. Will appear in Kupffer cells following rupture of caniculi. Can appear as finely granular pigment within in hepa- tocytes, which is common in human liver but much less common in rodents. Not a common xenobiotic response in rodents; more common in humans and monkeys.
17. Cholestasis
18. Mineralization (Vowles and Francis 2002; Kanel and Korula 2005) and by immunohistochemistry. Mineralization (Figure 20) Pathogenesis: Hypercalcemia secondary to diet or abnormal calcium metabolism; hepatocellular necrosis (dystrophic mineralization). Diagnostic features: Intra- or extracellular basophilic deposits, sometimes with calcification. Differential diagnosis: Artifact—hematoxylin stain deposits in clear spaces. Pigment deposits—may be tinctorially different from mineralization and often seen within macrophages. Intrabiliary accumulation of test compound or Iron/hemosiderin: Can be yellow to brown. May be finely granular. Usually appears intracellularly in hepatocytes. Porphyrin: Pigment is dense dark brown to re viewed with polarization is bright r located dark ‘‘Maltese cross.’’ Brilliant red fluorescence when frozen sections; fades with expo let light. Most often located in bile d canaliculi. Bile (cholestasis) (Figures 23–25): Appears as elongated pale green-b
19. Inclusions thus showing birefringence. Inclusions, Intranuclear, and Cytoplasmic (Figures 29–32) Synonyms: Inclusion bodies, intranuclear cytoplasmic invagi- nation, acidophilic inclusions, globular bodies. Pathogenesis: Protrusion of cytoplasm into an invagination of the hepatocyte nuclear membrane without the actual protrusion necessarily being present in the plane of section. Seen in spe- cific viral infections. Deposition of protein material within hepatocyte cytoplasm. Diagnostic features: Intranuclear inclusions are round, distinct, usually eccentrically located, and may partially or almost completely fill the nucleus. Contents of intranuclear inclusion bodies are often eosinophilic and may be granular or flocculent. Intracytoplasmic inclusions are round to oval, homo- genous, eosinophilic, and occur as single or multiple structures in the cytoplasm. Differential diagnosis: Enlarged nucleolus—one or more deeply basophilic structures in normal size nuclei. Viral inclusion bodies (cytomegalic virus, experi- mental viral infections). Cytoplasmic vacuole artifact—postmortem plasma influx (Li et al. 2003). plasmic inclusions such as Mallory bodies, lamellated, and crystalloid inclusions have been described in mice treated with different chemicals and in lysosomal storage diseases (Gebbia et al. 1985; Meierhenry et al. 1983; Rijhsinghani et al. 1980; Shio et al. 1982). Cytoplasmic vacuoles can occur in hepatocytes and endothelial cells in a postmortem time-dependent manner in fasted and non-fasted rats (Li et al. 2003). This artifact is espe- cially common in rats that are not exsanguinated at necropsy and the cytoplasmic vacuoles represent plasma influx into to affected cells (Figure 33). This artifact is more common in males than in females. Hypertrophy, Hepatocellular (Figures 34–41) Synonyms: Hepatocytomegaly. Pathogenesis: Metabolic enzyme induction causing increase in endoplasmic reticulum; increase in peroxisomes; increase in mitochondria. Diagnostic features: Enlarged hepatocytes may be tinctorially distinct. Cytoplasm may be homogeneous or granular. Zonal pattern of distribution (centrilobular, peripor- tal, midzonal) may be present. Involving most or all lobules. Loss of hepatocellular plate architecture is possible. Sinusoidal compression. Concurrent degeneration and/or single cell necrosis is possible. at Society of Toxicologic Pathology on August 8, 2013tpx.sagepub.comDownloaded from
20. Intrahepatocytic Erythrocytes
21. Intrahepatocytic Erythrocytes
22. Intrahepatocytic Erythrocytes FIGURE 7.—A–F, Series of images characterizing the lesion of ‘‘intrahepatocytic erythrocytes.’’ A, Low-magnification image showing the loca- tion of several areas containing intrahepatocytic erythrocytes near the edge of the liver (arrows; HE). B, Higher magnification of (A) illus- trating intrahepatocellular erythrocytes with some adjacent hepatocytes containing a decreased cytoplasmic density. (HE). C D, Higher Toxicologic Pathology 41: 151-180 (2013)
23. Hyaline Degeneration (Inclusions) High-Dose Male B6C3F1 Mouse Tx: Ethylene glycol
24. Hyaline Degeneration (Inclusions) High-Dose Male B6C3F1 Mouse Tx: Ethylene glycol
25. Hyaline Bodies
26. Hyaline Bodies
27. Hyaline Bodies
28. Plasma Influx This is an artifact
29. Crystals 1990). Crystals (Figures 26–28) Pathogenesis: Hyperlipidemia (cholesterol crystals), Chi313 (Ym1) protein (eosinophilic biliary crystals). Diagnostic features: Rhomboid or needle-like structures often birefringent under polarized light. Needle-like crystals in the mouse can be intracellular or extracellular and may be associated with intense eosinophilic epithelial cytoplasm and extracellular crystals of various sizes. ciety of Toxicologic Pathology on August 8, 2013
30. Crystals
31. Cytologic Alteration of necropsy during the day. Failure to accumulate glycogen because of inanition or abnormal glycogen retention may result from treatment-induced metabolic perturbations. Cytoplasmic Alteration (Figure 44) Synonyms: Cytoplasmic alteration, cytoplasmic change, granu- lar change, granular degeneration, hyaline degeneration, glyco- gen accumulation; ground glass change. Pathogenesis: Often xenobiotic-induced and may be associated with other forms of liver damage. Diagnostic features: Affected cells may show increased cytoplasmic gran- ularity, cell swelling, and eosinophilia. Differential diagnosis: to disturbance of cell m Diagnostic features: Cytoplasmic va centrally located Lobular location with increased c Differential diagnosis: Cytoplasmic va influx. Glycogen accum enlarged; cytopl Comment: Because of d rity, accumulation of i causes vacuolation and
32. Clear cell change – Glycogen accumulaJon In the INHAND document this change falls under the diagnostic category of Cytoplasmic Alteration A proposed alternative has been suggested by SEND for consideration: Rarefaction For example: Rarefaction, hepatocyte, increased, diffuse
33. Intracytoplasmic Glycogen Liver without Glycogen
34. PAS with diastase PAS
35. N M G L L G M M P RER Glycogen
36. Clear cell change – Glycogen accumulaJon
37. Normal glycogen accumulaJon Glycogen depleJon Glycogen
38. Normal glycogen accumulaJon Excessive glycogen Glycogen
39. Fatty Change at p- be or- in or al. ns. ns th es. re m, tic gi- a- to adaptive changes usually do not result in illness or death of rodents. Often these processes are dose and chemical related. Fatty Change Synonyms/subtypes: Lipidosis, vacuolation, lipid, macrovesi- cular and/or microvesicular steatosis, phospholipidosis.1 Pathogenesis: Perturbations in lipid metabolism and disposition. Diagnostic features: Macrovesicular fatty change (Figures 5 and 6). Hepatocytes contain a large well-defined single rounded vacuole within each cell. Nucleus and cytoplasm displaced to the periphery. A few hepatocytes may contain one or more smaller vacuoles. Microvesicular fatty change (Figure 7). Hepatocytes partially or completely filled with numerous small lipid vacuoles. Affected hepatocytes may have a ‘‘foamy’’ appearance. Small vacuoles do not normally displace the nucleus to the periphery in contrast to macrovesicular steatosis. Differential diagnosis: Hydropic degeneration—clear cytoplasm without nuclear displacement. Glycogen accumulation—irregular and poorly defined lacy clear spaces in the cytoplasm (rarefaction) usually with centrally located nuclei. Comment: There is a difference in preferred nomenclature among pathologists for this change. Based strictly on an FIGURE 1.—Gross appearance and tissue trimming recommendations for a normal rodent liver. Ref. to http://reni.item.fraunhofer.de/reni/trimming/ index.php. FIGURE 2.— Two-dimensional microarchitecture of the liver. FIGURE 3.—Rat liver. Hepatodiaphragmatic nodule. FIGURE 4.—Rat liver. Hepatodiaphragmatic nodule with intranuclear inclusions (chromatin). Higher magnification of Figure 3. FIGURE 5.—Rat liver. Macrovesicular fatty change. FIGURE 6.—Rat liver. Macrovesicular fatty change. Higher magnification of Figure 5. at Society of Toxicologic Pathology on August 8, 2013tpx.sagepub.comDownloaded from FIGURE 1.—Gross appearance and tissue trimming recommendations for a normal rodent liver. Ref. to http://reni.item.fraunhofer.de/reni/trimming/ index.php. FIGURE 2.— Two-dimensional microarchitecture of the liver. FIGURE 3.—Rat liver. Hepatodiaphragmatic nodule. FIGURE 4.—Rat liver. Hepatodiaphragmatic nodule with intranuclear inclusions (chromatin). Higher magnification of Figure 3. FIGURE 5.—Rat liver. Macrovesicular fatty change. FIGURE 6.—Rat liver. Macrovesicular fatty change. Higher magnification of Figure 5. at Society of Toxicologic Pathology on August 8, 2013tpx.sagepub.comDownloaded from 44S THOOLEN ET AL. TOXICOLOGIC PATHOLOGY
40. Oil-Red-O Stain for Lipid Mouse Liver
41. Fatty Change Zonal Focal
42. Vacuolated Focus Focal Fatty Change
43. Vacuolated Focus Focal Fatty Change
44. Focal Fatty Change
45. at p- be r- n or l. s. ns h s. re m, ic i- a- adaptive changes usually do not result in illness or death of rodents. Often these processes are dose and chemical related. Fatty Change Synonyms/subtypes: Lipidosis, vacuolation, lipid, macrovesi- cular and/or microvesicular steatosis, phospholipidosis.1 Pathogenesis: Perturbations in lipid metabolism and disposition. Diagnostic features: Macrovesicular fatty change (Figures 5 and 6). Hepatocytes contain a large well-defined single rounded vacuole within each cell. Nucleus and cytoplasm displaced to the periphery. A few hepatocytes may contain one or more smaller vacuoles. Microvesicular fatty change (Figure 7). Hepatocytes partially or completely filled with numerous small lipid vacuoles. Affected hepatocytes may have a ‘‘foamy’’ appearance. Small vacuoles do not normally displace the nucleus to the periphery in contrast to macrovesicular steatosis. Differential diagnosis: Hydropic degeneration—clear cytoplasm without nuclear displacement. Glycogen accumulation—irregular and poorly defined lacy clear spaces in the cytoplasm (rarefaction) usually with centrally located nuclei. Comment: There is a difference in preferred nomenclature Macrovesicular Fatty Change (Diffuse) Vehicle Male F344 Study: Kava kava extract Dx: Fatty change, diffuse +3
46. rodents. Often these processes are dose and chemical related. Fatty Change Synonyms/subtypes: Lipidosis, vacuolation, lipid, macrovesi- cular and/or microvesicular steatosis, phospholipidosis.1 Pathogenesis: Perturbations in lipid metabolism and disposition. Diagnostic features: Macrovesicular fatty change (Figures 5 and 6). Hepatocytes contain a large well-defined single rounded vacuole within each cell. Nucleus and cytoplasm displaced to the periphery. A few hepatocytes may contain one or more smaller vacuoles. Microvesicular fatty change (Figure 7). Hepatocytes partially or completely filled with numerous small lipid vacuoles. Affected hepatocytes may have a ‘‘foamy’’ appearance. Small vacuoles do not normally displace the nucleus to the periphery in contrast to macrovesicular steatosis. Differential diagnosis: Hydropic degeneration—clear cytoplasm without nuclear displacement. Glycogen accumulation—irregular and poorly defined lacy clear spaces in the cytoplasm (rarefaction) usually with centrally located nuclei. Comment: There is a difference in preferred nomenclature among pathologists for this change. Based strictly on an HE-stained section, a diagnosis of cytoplasmic vacuolation Vehicle Male F344 Study: Kava kava extract Dx: Fatty change, diffuse +3
47. Microvesicular – Zonal High-dose Male B6C3F1 Tx: Kava kava extract Dx: Centrilobular fatty change 4+ and necrosis
48. Microvesicular Fatty Change – Diffuse Female B6C3F1 Tx: 3,3’,4,4’-Tetrachloroazobenzene
49. Microvesicular – Diffuse
50. Diagnostic features: Macrovesicular fatty change (Figures 5 and 6). Hepatocytes contain a large well-defined single rounded vacuole within each cell. Nucleus and cytoplasm displaced to the periphery. A few hepatocytes may contain one or more smaller vacuoles. Microvesicular fatty change (Figure 7). Hepatocytes partially or completely filled with numerous small lipid vacuoles. Affected hepatocytes may have a ‘‘foamy’’ appearance. Small vacuoles do not normally displace the nucleus to the periphery in contrast to macrovesicular steatosis. Differential diagnosis: Hydropic degeneration—clear cytoplasm without nuclear displacement. Glycogen accumulation—irregular and poorly defined lacy clear spaces in the cytoplasm (rarefaction) usually with centrally located nuclei. Comment: There is a difference in preferred nomenclature among pathologists for this change. Based strictly on an HE-stained section, a diagnosis of cytoplasmic vacuolation of hepatocytes is a universally acceptable descriptive diagno- sis. Based on the experience of the observer, the specific mor- phological features of the cytoplasmic vacuolation may be Microvesicular Fatty Change – Focal
51. Phospholipidosis diet, vitamin A excess) in both animals and man. Special stains on cryostat sections can demonstrate fat (e.g., Oil red O or Sudan Black) (Jones 2002). Phospholipidosis2 Synonym: Cytoplasmic vacuolation, foam cells. Pathogenesis: Induced by xenobiotics with a cationic ampho- philic structure. Diagnostic features: Multiple irregular to round clear membrane-bound vacuoles. Tends to be a diffuse change affecting hepatocytes. nohistochemical techniques (Obert et al. 2007). This indicates that this vacuolation was due to accumulation of non- lysosomal neutral lipid. Cytoplasmic microvesiculation located centrally in hepatocytes that exhibit positive immuno- histochemical staining for LAMP-2 (Figure 17) but is nega- tive for Oil-Red-O and adipophilin is indicative of phospholipid accumulation (Obert et al. 2007). Amyloidosis (Figures 18 and 19) Pathogenesis: Cellular process related to misfolding of protein. Diagnostic features: Deposition of pale, homogeneous, amorphous eosi- nophilic material. Deposition often peri-sinusoidal, periportal, or involving blood vessel walls. Localization is extracellular.2 Electron microscopy or special staining needed for a definitive diagnosis. at Society of Toxicologic Pathology on August 8, 2013tpx.sagepub.comDownloaded from
52. Hepatic Hypertrophy
53. Hypertrophy thin y st n – e c – a affected cells (Figure 33). This artifact is more common in males than in females. Hypertrophy, Hepatocellular (Figures 34–41) Synonyms: Hepatocytomegaly. Pathogenesis: Metabolic enzyme induction causing increase in endoplasmic reticulum; increase in peroxisomes; increase in mitochondria. Diagnostic features: Enlarged hepatocytes may be tinctorially distinct. Cytoplasm may be homogeneous or granular. Zonal pattern of distribution (centrilobular, peripor- tal, midzonal) may be present. Involving most or all lobules. Loss of hepatocellular plate architecture is possible. Sinusoidal compression. Concurrent degeneration and/or single cell necrosis is possible. at Society of Toxicologic Pathology on August 8, 2013m
54. Increased Smooth Endoplasmic Reticulum Control Treated
55. Constitutive Enzyme Activity CYP 3A1
56. Enzyme Induction
57. Persistent Excessive Enzyme Induction
58. Persistent Excessive Enzyme Induction
59. Hypertrophy – Peroxisome Proliferation – n affected cells (Figure 33). This artifact is more common in males than in females. Hypertrophy, Hepatocellular (Figures 34–41) Synonyms: Hepatocytomegaly. Pathogenesis: Metabolic enzyme induction causing increase in endoplasmic reticulum; increase in peroxisomes; increase in mitochondria. Diagnostic features: Enlarged hepatocytes may be tinctorially distinct. Cytoplasm may be homogeneous or granular. Zonal pattern of distribution (centrilobular, peripor- tal, midzonal) may be present. Involving most or all lobules. Loss of hepatocellular plate architecture is possible. Sinusoidal compression. Concurrent degeneration and/or single cell necrosis is possible. Society of Toxicologic Pathology on August 8, 2013
60. Peroxisome Proliferation
61. Peroxisome Proliferation Ultrastructure Control Treated •  Hypolipidemics •  Clofibrate •  Gemfibrozil •  Methaphenilene •  Ibuprofen •  Diethylhexyl phthalate
62. Persistent Excessive Peroxisome Proliferation
63. Mitochondrial Hypertrophy
64. Atrophy enzyme induction, it is recommended that alternative forms of hepatocyte enlargement not be diagnosed as hepatocellu- lar hypertrophy. Hepatocellular Atrophy (Figures 42 and 43) Pathogenesis: Inanition, starvation, hemodynamic changes, or pressure atrophy from neoplasia. enlargement such as glycogen accumulation/retention, and even early necrosis (a.k.a. onconosis) may be difficult. In some cases special stains may be required to more clearly delineate the nature of the cytologic alteration. Based strictly on HE staining, a descriptive diagnosis of cytoplasmic alteration is recommended in lieu of interpretative diagnosis such as gran- ular degeneration and hyaline degeneration. However, there are some degenerative lesions, such as hydropic degeneration and at Society of Toxicologic Pathology on August 8, 2013tpx.sagepub.comDownloaded from th th ete lls nd ar o- Diagnostic features: Decreased size of hepatocytes. Small liver trabeculae with decreased cytoplasmic volume, close proximity of hepatocyte nuclei, close proximity of portal tracts, and increased basophilia. Hepatocyte nuclei may be smaller than normal. May have a zonal distribution. May be associated with hepatocellular degeneration and/or single cell necrosis. May be associated with increased sinusoidal size. Depletion of cytoplasmic glycogen. Differential diagnosis: THOOLEN ET AL. TOXICOLOGIC PATHOLOGY
65. Atrophy
66. Atrophy
67. Atrophy
68. Part 2 – Hepatobiliary Non-Neoplastic • Cystic Changes • Cystic degeneration (spongiosis hepatis) • Biliary cysts • Cell Death • Necrosis • Apoptosis • Ploidy
69. Cystic Degeneration on ge ng al. be ers nd n- ot of dy be caused by a number of xenobiotics with differing lobular localization and may be a precursor to hepatocyte necrosis (Gkretsi et al. 2007; Wang et al. 2007; Peichoto et al. 2006; Matsumoto et al. 2006; Chengelis 1988). Degeneration, Cystic (Figure 46 and 47) Synonyms: Spongiosis hepatis (traditional diagnostic term pre- ferred by many pathologists). Pathogenesis: Cystic enlargement of perisinusoidal stellate cells (Ito cells) particularly observed in aging rats. Diagnostic features: Multi-loculated cyst(s) lined by fine septa containing fine flocculent eosinophilic material (PAS-positive). The cysts are not lined by endothelial cells and do not compress the surrounding liver parenchyma. May be accompanied by occasional erythrocytes or leukocytes. May be observed within altered hepatic foci and liver tumors. Affected cells may be markedly enlarged. t Society of Toxicologic Pathology on August 8, 2013
70. Cystic Degeneration (Spongiosis hepatis)
71. Low-Dose Male F344 Tx: Styrene Acrylonitrile Dx: Cystic degeneration 2+
72. Low-Dose Male F344 Tx: Styrene Acrylonitrile Dx: Cystic degeneration 2+
73. Low Dose Female Sprague-Dawley Tx: Tetrachloroazobenzene Dx: Angiectasis
74. Low Dose Female Sprague-Dawley Tx: Tetrachloroazobenzene Dx: Angiectasis
75. Biliary Cysts sion) can be formed in rats after administration of 2, 3, 7, 8- tetrachloro-dibenzo-p-dioxin (Gopinath, Prentice, and Lewis 1987; Jones and Butler 1975). Eosinophilic cytoplasmic inclu- sions may be seen in affected hepatocyte nuclei because of cell membrane invaginations. Cysts, Biliary (Hepatic Cysts) (Figures 67–69) Pathogenesis: More common in aging animals occurs as a dilation of biliary structures. Diagnostic features: Range in size from small to very large. Single or multiple cysts. Macroscopically may contain clear to pale yellow fluid. May occur anywhere in the liver and may be unilocu- lar or multilocular. Multilocular cysts are divided into variably sized compartments by partial or complete connective tissue septa. Cyst walls are characteristically lined by flattened to cuboidal epithelium. May be mild compression of adjacent hepatic parenchyma. Differential diagnosis: Cystic degeneration—consists of markedly enlarged cells with finely flocculent pale eosinophilic cytoplasm. Angiectasis (Peliosis hepatis)—dilated vascular spaces lined by endothelial cells; may contain blood cells. Bile duct dilation—dilated bile ducts lined by cuboi- dal epithelium; not multiloculated. Parasitic cyst—may have thickened wall and contain Martellotto 1987). The cysts seen in polycystic disease are mul- tiple and seen diffusely throughout the liver and are of variable size but generally large compared to the smaller biliary cysts. C. Inflammatory Cell Infiltrates and Hepatic Inflammation (Hepatitis) Introduction A variety of focal, multifocal, and more generalized infiltra- tions of inflammatory cells are frequently present in liver tis- sue. Changes range from acute inflammatory cell infiltrate(s) or occasional aggregates of lymphocytes/lymphohistiocytic cells/foci of mononuclear cells without associated alterations of adjacent hepatocytes, to large panlobular patches of distinct hepatocyte necrosis accompanied by polymorphonuclear and mononuclear (lymphocytes, plasma cells, macrophages) cellu- lar infiltrates. ‘‘Mononuclear cell’’ can be used when there is a mixture of cell types (lymphocytes; less often macrophages and plasma cells) or the cell type is mononuclear but cannot be unequivocally identified in HE stain. If a cell type predomi- nates, then the infiltrate should be classified as lymphocytic, plasmacytic, or histiocytic. While etiological agents (e.g., bac- teria, virus, parasite) may be present, in most safety assessment studies the causes of significant inflammation are either cryptic or are attributed to a specific treatment regimen. Inflammatory reactions in the liver may be accompanied by oval cell and fibroblast proliferation and the propensity for hepatocellular proliferative responses to replace lost parenchyma. It is recommended that use of the diagnostic term ‘‘inflammation’’ for the liver should be used sparingly. Liver inflammation (hepatitis) is operationally defined as a constella- tion of changes that represent a severe and generalized liver reaction and would require multiple diagnostic terms to ade-
76. Biliary Cysts
77. Biliary Cysts
78. Biliary Cysts
79. Biliary Cysts
80. Biliary Cysts
81. Apoptosis – n . t – f – n Single Cell Necrosis (Apoptosis) (Figures 48–50) Diagnostic features: Affected hepatocytes may have condensed hyper- eosinophiliccytoplasmandasomewhatangularoutline. Not associated with an inflammatory response unless there is simultaneous necrosis. May occur spontaneously with one or two affected hepatocytes present in an occasional hepatic lobule. May be exacerbated by treatment. In standard HE-stained sections, apoptotic hepato- cytes (apoptotic bodies) are usually rounded with condensed cytoplasm. Rounded apoptotic bodies are typically surrounded by a clear halo. Fragments of nuclear material may be present within affected cells. Apoptotic bodies are frequently phagocytosized by adjacent normal cells including hepatocytes and macrophages. Differential diagnosis: Small foci of necrosis—typically cells are swollen and there is loss of membrane integrity; usually not rounded; less intensely stained than apoptotic bodies; may be accompanied by inflammatory cells. LEN ET AL. TOXICOLOGIC PATHOLOGY
82. Single Cell Necrosis – Apoptosis
83. Apoptosis
84. Apoptosis in a Liver with Increased Peroxisomes in Hepatocytes
85. Necrosis necrosis, may occur within hours after exposure to a xenobio- tic, and should not be diagnosed as single cell necrosis (apop- tosis). A more appropriate diagnosis for this situation is focal necrosis (see the following). Necrosis, Focal/Multifocal (Figures 51–53) Diagnostic features: Single or multiple foci of a few pale staining hepatocytes. Usually retain normal morphological outline. May be associated with inflammation. May have an irregular distribution but can also occur in thesubcapsularareaswithminimalornoinflammation. Early lesions typically consist of three or four hepa- tocytes, but as the lesions progress more hepatocytes may be involved. Subcapsular necrosis may sometimes be observed in combination with hypertrophy. Differential diagnosis: Foci of extramedullary hematopoiesis—mature and/ or immature erythroid and myeloid cell aggregates without accompanying hepatocyte necrosis. Foci of inflammatory cell infiltrate—aggregates of cells, usually mononuclear cells, in absence of obvi- ous hepatocellular necrosis. Infectious disease (MHV, Ectromelia, Clostridium pilliforme, Helicobacter hepaticus, Parvo virus, Noro virus)—a spectrum of acute to chronic active inflammation, degenerative, and proliferative changes specific for the infectious disease entity. Comment: Some pathologists use focal for both focal and mul- seen after anoxia, or exposure to tannic acid, chloroform, or other hepatotoxic agents (Gopinath, Prentice, and Lewis 1987). This zone (Rappaport zone 3) is particularly vulnerable to ischemic damage because of its low oxygen gradient and generation of toxic metabolites due to high content of xenobio- tic metabolizing enzymes (Comporti 1985; Walker, Racz, and McElligott 1985). Diagnostic features: Early necrotic hepatocytes are swollen. Cytoplasm has increased eosinophilia. Nucleus undergoing lysis, not pyknosis. May have a minimal associated inflammatory reaction. Can be accompanied by glycogen depletion, hydro- pic degeneration, fatty change, hemorrhage, and ‘‘ballooning’’ of hepatocytes. Midzonal (Figures 60–61) This necrosis is the least common form of zonal necrosis and is mediated by specific toxicants (e.g., furan, concavalin-A, beryllium) (Wilson et al. 1992; Boyd 1981; Seawright 1972; Satoh et al. 1996; Cheng 1956). The location is considered specific and has a metabolic basis. Diagnostic features: Seen as a band of swollen and eosinophilic cells intermediate to the central vein (zone III) and the por- tal triad (zone I). Nucleus undergoing lysis. Two to three cells in thickness in the middle of the lobule. Periportal (Figure 62) Midzonal ul- al ti- ar be ry en on 5; m of en Satoh et al. 1996; Cheng 1956). The location is considered specific and has a metabolic basis. Diagnostic features: Seen as a band of swollen and eosinophilic cells intermediate to the central vein (zone III) and the por- tal triad (zone I). Nucleus undergoing lysis. Two to three cells in thickness in the middle of the lobule. Periportal (Figure 62) Hepatic necrosis in the periportal zone is observed follow- ing a variety of agents (e.g., phosphorus, ferrous sulphate, allyl alcohol) (Kanel and Korula 2005; Atzori and Congiu 1996; Sasse and Maly 1991). Affected cells may encircle the portal tract (Popp and Cattley 1991) and may be associated with inflammatory and other changes (Ward, Anver, et al. 1994; Ward, Fox, et al. 1994; NTP Technical Report on the Toxicology and Carcinogenesis Studies of a Binary Mixture 2006; NTP Technical Report on the Toxicology and Carcino- genesis Studies of 2, 3, 7, 8-tetracholorodibenzo-p-dioxin 2006). Diagnostic features: Swollen and/or eosinophilic hepatocytes may com- pletely encircle the portal tract. Nucleus undergoing lysis. May be accompanied by periportal inflammation, fibro- sis, bile duct proliferation, and oval cell hyperplasia. t Society of Toxicologic Pathology on August 8, 2013 Focal, MulJfocal tic, and should not be diagnosed as single cell necrosis (apop- tosis). A more appropriate diagnosis for this situation is focal necrosis (see the following). Necrosis, Focal/Multifocal (Figures 51–53) Diagnostic features: Single or multiple foci of a few pale staining hepatocytes. Usually retain normal morphological outline. May be associated with inflammation. May have an irregular distribution but can also occur in thesubcapsularareaswithminimalornoinflammation. Early lesions typically consist of three or four hepa- tocytes, but as the lesions progress more hepatocytes may be involved. Subcapsular necrosis may sometimes be observed in combination with hypertrophy. Differential diagnosis: Foci of extramedullary hematopoiesis—mature and/ or immature erythroid and myeloid cell aggregates without accompanying hepatocyte necrosis. Foci of inflammatory cell infiltrate—aggregates of cells, usually mononuclear cells, in absence of obvi- ous hepatocellular necrosis. Infectious disease (MHV, Ectromelia, Clostridium pilliforme, Helicobacter hepaticus, Parvo virus, Noro virus)—a spectrum of acute to chronic active inflammation, degenerative, and proliferative changes specific for the infectious disease entity. Comment: Some pathologists use focal for both focal and mul- other hepatotoxic agents (Gopinath, Prentice, and Lewis 1987). This zone (Rappaport zone 3) is particularly vulnerable to ischemic damage because of its low oxygen gradient and generation of toxic metabolites due to high content of xenobio- tic metabolizing enzymes (Comporti 1985; Walker, Racz, and McElligott 1985). Diagnostic features: Early necrotic hepatocytes are swollen. Cytoplasm has increased eosinophilia. Nucleus undergoing lysis, not pyknosis. May have a minimal associated inflammatory reaction. Can be accompanied by glycogen depletion, hydro- pic degeneration, fatty change, hemorrhage, and ‘‘ballooning’’ of hepatocytes. Midzonal (Figures 60–61) This necrosis is the least common form of zonal necrosis and is mediated by specific toxicants (e.g., furan, concavalin-A, beryllium) (Wilson et al. 1992; Boyd 1981; Seawright 1972; Satoh et al. 1996; Cheng 1956). The location is considered specific and has a metabolic basis. Diagnostic features: Seen as a band of swollen and eosinophilic cells intermediate to the central vein (zone III) and the por- tal triad (zone I). Nucleus undergoing lysis. Two to three cells in thickness in the middle of the lobule. Periportal (Figure 62) Centrilobular Subcapsular necrosis may sometimes be observed in combination with hypertrophy. Differential diagnosis: Foci of extramedullary hematopoiesis—mature and/ or immature erythroid and myeloid cell aggregates without accompanying hepatocyte necrosis. Foci of inflammatory cell infiltrate—aggregates of cells, usually mononuclear cells, in absence of obvi- ous hepatocellular necrosis. Infectious disease (MHV, Ectromelia, Clostridium pilliforme, Helicobacter hepaticus, Parvo virus, Noro virus)—a spectrum of acute to chronic active inflammation, degenerative, and proliferative changes specific for the infectious disease entity. Comment: Some pathologists use focal for both focal and mul- tifocal, referring to the nature of the lesion rather than its actual distribution. A severity grade can be used to reflect the multi- focal nature of the lesion. Focal, multifocal, and subcapsular necrosis is occasionally seen in untreated rodents and may be a terminal event potentially due to hypoxic change secondary to impaired blood flow. Subcapsular necrosis has also been reported from direct pressure secondary to gastric distention and from some types of restraint (Parker and Gibson 1995; Nyska et al. 1992) Necrosis, Zonal (Centrilobular, Midzonal, Periportal, Diffuse) Pathogenesis: Secondary to direct or indirect damage from xenobiotic exposure; tissue anoxia. Centrilobular (Figures 54–59) Midzonal (Figures 60–61) This necrosis is the least common form of zonal necrosis and is mediated by specific toxicants (e.g., furan, concavalin-A, beryllium) (Wilson et al. 1992; Boyd 1981; Seawright 1972; Satoh et al. 1996; Cheng 1956). The location is considered specific and has a metabolic basis. Diagnostic features: Seen as a band of swollen and eosinophilic cells intermediate to the central vein (zone III) and the por- tal triad (zone I). Nucleus undergoing lysis. Two to three cells in thickness in the middle of the lobule. Periportal (Figure 62) Hepatic necrosis in the periportal zone is observed follow- ing a variety of agents (e.g., phosphorus, ferrous sulphate, allyl alcohol) (Kanel and Korula 2005; Atzori and Congiu 1996; Sasse and Maly 1991). Affected cells may encircle the portal tract (Popp and Cattley 1991) and may be associated with inflammatory and other changes (Ward, Anver, et al. 1994; Ward, Fox, et al. 1994; NTP Technical Report on the Toxicology and Carcinogenesis Studies of a Binary Mixture 2006; NTP Technical Report on the Toxicology and Carcino- genesis Studies of 2, 3, 7, 8-tetracholorodibenzo-p-dioxin 2006). Diagnostic features: Swollen and/or eosinophilic hepatocytes may com- pletely encircle the portal tract. Nucleus undergoing lysis. Periportal Diffuse (Figures 63 and 64) Synonym: Massive necrosis, panlobular necrosis. Diagnostic features: Necrosis involving a large portion of a liver lobe. May be associated with torsion of a liver lobe. May be randomly distributed throughout the liver without a specific lobular localization. Differential diagnosis: Autolysis—loss of microscopic tissue structure and stain affinity; pale eosinophilic staining and absence Pathogenesis: Duplication of nuclear material in absence o cytokinesis. Variations in nuclear size and ploidy (karyome galy and/or anisokaryosis) are common in aging rodents. Diagnostic features: Hepatocytes with either two or more nuclei or with a single enlarged nucleus which may be tetraploid or octaploid. Polyploid hepatocytes are frequently larger than adja- cent diploid hepatocytes. Anisokaryosis is randomly distributed in the hepatic lobule with more affected hepatocytes in the centri- lobular region. 18S THOOLEN ET AL. TOXICOLOGIC PATHOLOG Diffuse
86. Necrosis
87. Necrosis, Focal
88. Necrosis
89. Centrilobular Hepatocyte Necrosis
90. Centrilobular Hepatocyte Necrosis
91. Centrilobular Hepatocyte Necrosis Subchronic study B6C3F1 Tx: Divinyl benzene
92. Centrilobular Hepatocyte Necrosis Subchronic study B6C3F1 Tx: Divinyl benzene
93. Periportal Necrosis
94. Mid-lobular Necrosis
95. Severe Necrosis with Bridging Male F344 Rat High-dose Tx: Coumarin Dx: Coagulation necrosis
96. Centrilobular Necrosis with Hemorrhage and Mineralization Acute necrosis Tx: Bromobenzene
97. Centrilobular Necrosis with Hemorrhage and Mineralization Acute necrosis Tx: Bromobenzene
98. Necrosis
99. Teutsch, et al. 1999. Hepatology 29:494-505
100. Thrombosis of a group of small blood vessels. It can be observed in transgenic mouse models (Srinivasan et al. 2003; Bourdeau et al. 2001) or related to xenobiotic administration in rats and mice (Robison et al. 1984; Kim et al. 2004). It can be found as an incidental find- ing in aging mice and is sometimes associated with hepatocellu- lar neoplasms (Harada et al. 1996, 1999). Angiectasis can be chemically induced (Bannasch, Wayss, and Zerban 1997) and has been suggested to be preneoplastic in some animal models. Thrombosis (Figure 88) Pathogenesis: Activation of the coagulation system associated with arteritis or phlebitis or secondary to atrial thrombosis. Diagnostic features: It is characterized by the formation of a thrombus within the lumen of a blood vessel, like sinusoids and central veins. Amorphous mass attached to the endothelium or free within the blood vessel lumen (due to plane of section). Contains fibrin, platelets, and entrapped blood cells. Damaged endothelium can be seen. May occur with histiocytic sarcoma in rats or mice. Differential diagnosis: Postmortem clot. Necrotic area of tissue—loss of microscopic tissue structure and stain affinity; pale eosinophilic stain- ing, and absence of nuclear detail. Hepatocellular necrosis resulting from direct toxicity may have a diffuse or lobular distribution but also may be accompanied by infarction; not mutually exclusive. Comment: Aside from torsion of liver lobes, which can occur spontaneously in rodents, infarction is a very rare lesion that can be induced only under very specific experimental condi- tions. The combined injection in mice of NG-monomethyl-L- arginine and aspirin after lipopolysaccharide exposure resulted in significant hepatocellular enzyme release, characterized his- tologically by intravascular thrombosis with diffuse infarction and necrosis (Harbrecht et al. 1994). Intraperitoneal injections in rats of vasoconstrictor xenobiotics such as phenylephrine produced infarcts of the spleen regularly and infarcts of the liver occasionally (Levine and Sowinski 1985). Isolated perfu- sion with 1.0 g/kg of the cytotoxic xenobiotic 5-FU or hyperthermia of 41 degrees C Â 10 min resulted in 90% to 100% mortality in rats, with extensive, patchy necrosis, and infarction on histologic examination (Miyazaki et al. 1983). Endothelial Cell Hypertrophy/Karyomegaly3 (Figure 91) Synonyms: Endothelial cell enlargement, cytomegaly. Introduction: This is a relatively new diagnostic entity. Because of the difficulty of identifying specific sinusoidal cell 3 The examples provided were confirmed with special stains (not shown). However, based solely on HE staining, a diagnosis of ‘‘sinusoidal cell hypertrophy/karyomegaly’’ is appropriate. at Society of Toxicologic Pathology on August 8, 2013tpx.sagepub.comDownloaded from oids and 950). cula- gen- sular ding aces ken- ypes d of mal’’) ards, aged ed in 967) and mans werdt er of oids 973; ation enic 1) or ison find- ellu- n be Comment: There are several potential mechanisms leading to liver thrombosis. Activation of the coagulation system associ- ated with fibrin deposits and hypoxia located in the centrilob- ular sinusoids was reported to occur in the livers of rats exposed to monocrotaline (MCT) (Copple et al. 2002). It was suggested that the fibrin thrombi were formed following chemical-induced hepatic endothelial cell damage. In studying an endotoxin-exposure model, it was suggested that the noted focal and random hepatocellular necrosis was caused by circu- latory disturbances due to fibrin thrombi in clusters of adjacent sinusoids. Using a rat model of 2-butoxyethanol induced hemo- lytic anemia associated with systemic thrombosis, fibrin thrombi were noted in the central vein and sinusoids of the liver, in addition to the presence of thrombi seen in several other organs (Ramot et al. 2007). Infarction (Figures 89 and 90) Pathogenesis: Interruption of blood flow in a major vessel. Torsion of hepatic lobe. Diagnostic features: Extensive area of necrosis may be associated with inflammation. The necrosis does not have acinar pattern. Differential diagnosis: Hepatocellular necrosis resulting from direct toxicity may have a diffuse or lobular distribution but also may be accompanied by infarction; not mutually exclusive. Comment: Aside from torsion of liver lobes, which can occur HE HEPATOBILIARY SYSTEM 25S Infarction
101. Karyocytomegaly and/or Multinucleated Hepatocytes (Ploidy) Diffuse (Figures 63 and 64) Synonym: Massive necrosis, panlobular necrosis. Diagnostic features: Necrosis involving a large portion of a liver lobe. May be associated with torsion of a liver lobe. May be randomly distributed throughout the liver without a specific lobular localization. Differential diagnosis: Autolysis—loss of microscopic tissue structure and stain affinity; pale eosinophilic staining and absence of nuclear detail. Torsion of a liver lobe—Affects an entire liver lobe, loss of microscopic structure. Infarction—usually an angularly shaped wedge or area of tissue necrosis; may be associated with a nearby thrombus. Comment: Zonal necrosis is typically associated with expo- sure to xenobiotics that either directly damage hepatocytes or cause damage following metabolic activation by endo- genous or induced enzymes. There is often a concentration gradient within the hepatic lobule with more extensive lob- ular involvement associated with higher doses of the toxic agent. Hepatocellular necrosis can occur spontaneously in rodents or be induced by xenobiotics, toxins, or following treatment at high dosages with associated tissue anoxia, circulatory derangements, and biliary stasis. Necrosis (centrilobular, mid- zonal, periportal) might be accompanied by other histological Pathogenesis: Duplication of nuclear material in absence of cytokinesis. Variations in nuclear size and ploidy (karyome- galy and/or anisokaryosis) are common in aging rodents. Diagnostic features: Hepatocytes with either two or more nuclei or with a single enlarged nucleus which may be tetraploid or octaploid. Polyploid hepatocytes are frequently larger than adja- cent diploid hepatocytes. Anisokaryosis is randomly distributed in the hepatic lobule with more affected hepatocytes in the centri- lobular region. Differential diagnosis: Hepatocellular neoplasia—mass or expansile prolif- eration of hepatocytes with distortion or loss of lobu- lar architecture. Hepatocellular hypertrophy (enzyme induction)— increase in cytoplasmic volume not typically associ- ated with increased nuclear size or number. Comment: Karyocytomegaly is a reflection of hepatocyte polyploidy that occurs when there is duplication of nuclear material in the absence of cytokinesis. The result is an increase in the number of diploid nuclei per hepatocyte or an increase in the ploidy level of a single hepatocyte nucleus. Polyploidy increases with age in some strains of mice as well as following some treatment regimens resulting in hepatocytomegaly as well as karyomegaly (Harada et al. 1996). Variations in cell size as well as in nuclei and polyploidy are also common in 18S THOOLEN ET AL. TOXICOLOGIC PATHOLOGY
102. Extreme Hepatocytomegaly
103. Multinucleated Hepatocytes
104. Part 3- Hepatobiliary Non-Neoplastic • Infiltration – Inflammation • Toxic Hepatopathy • Vascular Changes • Increased Mitosis • Foci of Cellular Alteration • Hyperplasia • Cholangiofibrosis
105. Infiltration – Inflammation
106. Small Focal Lesions Female Swiss Mouse Subchronic Study Tx: Oxazepam
107. Small Focal Lesions This is a common lesion seen in rodent toxicity studies.
108. Small Focal Lesions Prechronic Study B6C3F1 Mouse Control Female
109. Small Focal Lesions Female B6C3F1 Untreated Prechronic Study Dx: Within normal limits Female B6C3F1 Untreated Prechronic Study Dx: Inflammation
110. Small Focal Lesions
111. Small Focal Lesions
112. Small Focal Lesions Focal mononuclear cell aggregates? Microgranulomas? Focal cellular infiltrates? Hematopoietic cell proliferation?
113. Small Focal Lesions Focal mononuclear cell aggregates? Microgranulomas? Focal cellular infiltrates? Hematopoietic cell proliferation? Control Female Sprague Dawley Prechronic Study Dx: InflammaJon, chronic 1+ Focal neutrophilic infiltrate associated with hepatocyte necrosis
114. Hematopoietic Cell Proliferation
115. Hematopoietic Cell Proliferation
116. Hematopoietic Cell Proliferation
117. Hematopoietic Cell Proliferation
118. Granulomatous Inflammation
119. Chronic Inflammation High-dose Male (#434) F344 Rat Tx: Coumarin Dx: Fibrosis
120. High-dose Male (#394) F344 Rat Tx: Coumarin Dx: Coagulation Necrosis
121. Cirrhosis – Multiple Nodules of Hepatocyte Hyperplasia Separated by Scarring and Chronic Inflammation and Oval Cell Proliferation Treated Female Sprague Dawley Hyperplasia (Regeneration) In a chronic inflammatory situation, there will probably be a constellations of changes.
122. Chronic Inflammation F344 Rat Tx: Direct Blue 6 for 90 days Dx: Cirrhosis (fibrosis) regenerative nodules
123. Toxic Hepatopathy Toxic hepatopathy is a general diagnostic term used when a constellation of microscopic changes secondary to chronic toxicity is present. Changes include hepatocyte degeneration, bile duct and oval cell hyperplasia, pigment deposition, fibrosis, and nodular hyperplasia. Female Sprague Dawlely High-dose Tx: PCB Mixture Dx: Toxic hepatopathy
124. Toxic Hepatopathy Toxic hepatopathy is a general diagnostic term used when a constellation of microscopic changes secondary to chronic toxicity is present. Changes include hepatocyte degeneration, bile duct and oval cell hyperplasia, pigment deposition, fibrosis, and nodular hyperplasia. Female Sprague Dawlely High-dose Tx: PCB Mixture Dx: Toxic hepatopathy
125. Toxic Hepatopathy Female Sprague Dawlely High-dose Tx: PCB Mixture Dx: Toxic hepatopathy Portal fibrosis
126. Toxic Hepatopathy Female Sprague Dawlely High-dose Tx: PCB Mixture Dx: Toxic hepatopathy Hepatocyte, multinucleated 3+
127. Congestion vs Hemorrhage
128. Passive Congestion large molecules but provide a barrier to blood cells. Kupffer cells reside in the lumen of the sinusoids and are anchored to their wall. The morphological aspect of the hepatic pathology during circulatory disorders depends on the location of the vascular structure being affected (i.e., lobular sinusoids, the outflow hepatic vein, or the inflow portal vein). Congestion (Figure 85) Synonym: Chronic passive congestion. Pathogenesis: Circulatory failure, typically right-sided heart failure. Diagnostic features: Increase prominence (number) of erythrocytes in the capillary bed or larger vessels of an organ. No appreciable distention (angiectasis) of the vessel wall. Diagnosis often correlates with gross observation (e.g., reddened, darkened focus). May be associated with centrilobular necrosis. Differential diagnosis: Angiectasis—dilated vascular spaces lined by endothelial cells; dilated vascular channels and spaces frequently contain erythrocytes. Massive necrosis. Hemorrhage-irregular patchy lakes of blood not con- tained within defined vascular channels. Autolysis-altered cellular texture and loss of staining intensity. 1. Cystic (‘‘Phlebectatic’’)—Focal dilation (disten- sion) of endothelial lined channels (photographic presentation contributed by Hardisty et al. 2007). Can be an isolated lesion or have a multicentric form. The lacunae are densely packed with blood and are coated by a single layer of endothelium and separated from one another by cords of liver parenchyma (Bannasch, Wayss, and Zerban 1997). The endothelial cells appear to be unal- tered, and there is no increase of mitotic figures. The tissue adjacent to the dilated sinusoids is well preserved and free of necrotic cells. 2. Cavernous (‘‘Parenchymal’’)—The peliotic cysts arenot, orareonly partially,linedbyendothelium. Thus, the cysts involve not only the sinusoidal lumen, but also the space of Disse, and the blood comes in direct contact with the neighboring par- enchymal cells. The parenchyma undergoes focal necrosiswithout a zonaldistribution.Thislesionis much less likely to be preneoplastic and a few tox- ins have been shown to induce the lesion. When endothelial lining is absent, the term Peliosis Hepatis instead of Angiectasis is indicated. Differential diagnosis: Hemangioma—expansile structure lined by flattened endothelial cells; may be associated with parenchy- mal compression. Cystic degeneration (Spongiosis hepatis)—cavities are not filled with blood but with a finely flocculent acidophilic material. Comment: Angiectasis is a cystic or cavernous widening of the liver sinusoids that can occur in a variety of pathological
129. Angiectasis vein, which carries venous blood that is largely depleted of oxygen, and relatively minor (about 25%) arterial blood sup- ply, via the hepatic artery. The portal blood contains toxic materials absorbed in the intestine, and therefore the liver is the first tissue to be exposed to toxic substances that have been absorbed through the gastro-intestinal tract. Within the hepatic parenchyma, the hepatocytes are in intimate contact with the sinusoidal capillaries, which are car- rying the mixture of blood originating from ramifications of the portal vein and hepatic artery to the central vein. The sinusoids are lined by modified endothelial cells containing fenestrations, which allow passage of lipoproteins and other large molecules but provide a barrier to blood cells. Kupffer cells reside in the lumen of the sinusoids and are anchored to their wall. The morphological aspect of the hepatic pathology during circulatory disorders depends on the location of the vascular structure being affected (i.e., lobular sinusoids, the outflow hepatic vein, or the inflow portal vein). Congestion (Figure 85) Synonym: Chronic passive congestion. Pathogenesis: Circulatory failure, typically right-sided heart failure. Diagnostic features: Increase prominence (number) of erythrocytes in the capillary bed or larger vessels of an organ. No appreciable distention (angiectasis) of the vessel wall. Diagnosis often correlates with gross observation (e.g., reddened, darkened focus). May be associated with centrilobular necrosis. Angiectasis (Figures 86 and 87) Synonyms: Peliosis hepatis, telangiectasis, sinusoidal dilation. Pathogenesis: Perturbations in blood flow and/or drainage; weakening of sinusoidal walls. Diagnostic features: Macroscopically—seen on the surface as blood- filled, thin walled cavities projecting above the sur- face (Bannasch et al. 1997). Microscopically—There are two morphological types, as follows: 1. Cystic (‘‘Phlebectatic’’)—Focal dilation (disten- sion) of endothelial lined channels (photographic presentation contributed by Hardisty et al. 2007). Can be an isolated lesion or have a multicentric form. The lacunae are densely packed with blood and are coated by a single layer of endothelium and separated from one another by cords of liver parenchyma (Bannasch, Wayss, and Zerban 1997). The endothelial cells appear to be unal- tered, and there is no increase of mitotic figures. The tissue adjacent to the dilated sinusoids is well preserved and free of necrotic cells. 2. Cavernous (‘‘Parenchymal’’)—The peliotic cysts arenot, orare only partially,linedbyendothelium. Thus, the cysts involve not only the sinusoidal lumen, but also the space of Disse, and the blood comes in direct contact with the neighboring par- enchymal cells. The parenchyma undergoes focal necrosiswithout a zonaldistribution.Thislesionis much less likely to be preneoplastic and a few tox- ins have been shown to induce the lesion. When endothelial lining is absent, the term Peliosis Hepatis instead of Angiectasis is indicated. Differential diagnosis: 24S THOOLEN ET AL. TOXICOLOGIC PATHOLOGY
130. Angiectasis Female control F344 Rat Diet restriction study Dx: Angiectasis
131. Female control F344 Rat Diet restriction study Dx: Angiectasis
132. Female control F344 Rat Diet restriction study Dx: Angiectasis
133. Treated Male B6C3F1 Tx: Tetrafluoroethylene Dx: Angiectasis Angiectasis
134. Angiectasis Treated Male B6C3F1 Tx: Tetrafluoroethylene Dx: Angiectasis
135. Increased Mitoses
136. Male F344 Tx: acetaminophen for 14 days
137. Male F344 Tx: acetaminophen for 14 days
138. Foci of Cellular Alteration of the proportions of each. Because of this diverse set of diagnostic opinions regarding focus subtypes, the pathologist is encouraged to describe the morphological features of documented foci in detail, especially if they are altered by treatment. Synonyms: Areas of cellular alteration; focus of altered hepatocytes; hyperplastic focus; preneoplastic focus; enzyme altered focus; phenotypically altered focus. Pathogenesis: A localized proliferation of hepatocytes pheno- typically different from surrounding hepatocyte parenchyma. Diagnostic features: May occasionally be observed grossly as small white foci on the liver surface, but not round nodules. Size may range from less than one lobule to multiple lobules in diameter. Circular or ovoid shape; irregular formed foci may occur. Distinguished into types of foci by virtue of tinctorial variation, size of hepatocytes, and textural appear- ances from surrounding parenchyma. May be subclassified based on predominant cell type. The fact that 80% of the focus is composed of one morphologic cell type (basophilic, eosinophilic, etc.) or a mixed cell type. Normally no or only minimal compression of the sur- rounding liver tissue. Liver plates merge imperceptible with surrounding hepatic parenchyma; nevertheless foci are sharply demarcated from the adjacent normal hepatocytes by the appearance and staining reaction of its cells. Lobular architecture preserved. homogeneously staining cytoplasmic basophilia due to abundant free ribosomes. Cells may be pleomorphic with enlarged vesiculated nuclei and prominent nucleoli. Dissociation of cells may occur. Mitotic figures may occur. Basophilic, tigroid (Figure 95). Cells are usually smaller; enlarged cells may occur. Cells are often arranged as tortuous cords. Cells display large abundant basophilic bodies often arranged in clumps or long bands with striped pattern in paranuclear or peripheral regions of cytoplasm (due to increased rough endoplasmic reticulum). Mitotic rate may be increased. Basophilic, NOS (Figure 96). Foci that are not clearly tigroid or diffusely basophilic. Peliosis or spongiosis may occur within these foci. Basophilic (no further classification in mice) (Figure 97). Consist of cells larger or smaller than normal hepato- cytes, in general they are smaller. Cytoplasm exhibits distinct basophilia due to free ribosomes or rough endoplasic reticulum. Often cells contain obvious glycogen. Intracytoplasmic basophilic clumps with relatively clear intervening cytoplasm or the cytoplasmic baso- philia may be distributed homogeneously. Vascular pseudo-invasion may be present. Eosinophilic cytoplasmic inclusions may be found occasionally within hepatocytes. at Society of Toxicologic Pathology on August 8, 2013tpx.sagepub.comDownloaded from alteration with a description in the pathology narrative. In some laboratories diagnosis of ‘‘increased mitoses’’ is used. Focus of Cellular Alteration Introduction: Foci of cellular alteration are common in rodent studies greater than duration of twelve months and may be seen in short duration toxicity studies following exposure to certain xenobiotics. Foci of cellular alteration can be iden- tified by special stains. In HE-stained slides they may be subclassified based on the predominant cell type present. Diagnosis of the mixed cell subtype of altered hepatic focus varies among different laboratories. One viewpoint defines a mixed focus of cellular alteration as consisting of a combina- tion of basophilic, vacuolated, eosinophilic, and/or clear cell hepatocytes without a predominant cell type. An alternative viewpoint defines a mixed cell focus as containing any two phenotypes of cells in approximately a 50%/50% proportion. Others regard a ‘‘true’’ mixed focus as one that contains clearly identified basophilic and eosinophilic cells regardless of the proportions of each. Because of this diverse set of diagnostic opinions regarding focus subtypes, the pathologist is encouraged to describe the morphological features of documented foci in detail, especially if they are altered by treatment. Portal areas and central veins not present in small foci but can be seen in larger foci. Sinusoids within focus may be compressed, so typical parenchymal plates are difficult to detect. Tortuous hepatic cords may occur due to increased number of cells. Size of cells and cytoplasmic tinctorial variation depend on type of focus. Normally absence of cellular atypia. Cystic degeneration (spongiosis hepatis) and angiectasis (peliosis hepatis) may occur within foci of altered cells. Cytoplasmic lipid may be present. Intracytoplasmic inclusions of various types may be present. Basophilic (Figures 93–97) Basophilic, diffuse (Figures 93 and 94). Hepatocytes of normal size or slightly enlarged with homogeneously staining cytoplasmic basophilia due to abundant free ribosomes. Cells may be pleomorphic with enlarged vesiculated nuclei and prominent nucleoli. Dissociation of cells may occur. Mitotic figures may occur. Vol. 38, No. 7S, 2010 LESIONS OF THE HEPATOBILIARY SYSTEM 27S Basophilic focus Eosinophilic focus Clear cell focus Mixed focus Vacuolated focus Amphophilic focus Tigroid focus
139. Foci of cellular alteration occur spontaneously in older rodents and when induced by treatment may occur in younger rodents. They are regarded as preneoplastic lesions by many because they are induced by known hepatocarcinogens and they temporally occur before liver tumors develop.
140. Basophilic Foci B6C3F1 Mouse Tx: Diethylnitrosamine
141. Basophilic Focus
142. Basophilic Focus
143. Basophilic Focus
144. Basophilic Focus F344 Rat Periportal location
145. Basophilic Focus Control F344 Rat Focus surrounds a central vein with extramedullary hematopoiesis
146. Basophilic Focus
147. Basophilic Focus
148. Basophilic Focus
149. Eosinophilic Focus F344 Rat Rat had LGL leukemia
150. Eosinophilic Focus of Cellular AlteraJon
151. Eosinophilic Focus
152. Eosinophilic Foci
153. Clear Cell Focus Female F344 Rat
154. Clear Cell Focus Female F344 Rat
155. Clear Cell Focus
156. Mixed Cell Foci
157. Mixed Cell Focus Treated Male F344 Rat
158. Mixed Cell Focus
159. Mixed Cell Focus Treated Female Sprague Dawley Rat
160. Mixed Cell Focus Treated Female Sprague Dawley Rat
161. Basophilic Focus with Fatty Change Untreated Male F344 Rat
162. Basophilic Focus with Fatty Change Untreated Male F344 Rat
163. Vacuolated Focus?
164. Focus of Cellular AlteraJon
165. Basophilic Focus of Cellular Alteration Vehicle Female Sprague Dawley
166. Basophilic Focus – Homogeneous Pattern
167. Basophilic Focus – Tigroid Pattern
168. Basophilic Focus – Cresyl Violet Stain
169. Amphophilic Focus
170. Glutathione S-Transferase pi
171. Tension Lipidosis Associated with attachment of falciform ligament
172. Tension Lipidosis Associated with attachment of falciform ligament
173. Regenerative Hyperplasia sia be in these nodules is increased in comparison with surrounding parenchyma and the lesion is glutathione S-transferase pla- cental form (GSTP) immunonegative. Very early non-regenerative hyperplasia may be the size of small foci of cellular alteration and are identified by their altered growth pattern and tinctorial similarity to surrounding parenchyma (see Figure 109). Hyperplasia, Hepatocellular,Regenerative (Figures 111–113) Synonyms: Hyperplasia, hepatocellular; hyperplasia, regenera- tive; hyperplasia, nodular; regeneration, nodular. Pathogenesis: A nodular regenerative response to prior or con- tinuous hepatocellular damage. Diagnostic features: Focal or multifocal (nodular) appearance. Lesion may reach several millimeters in diameter. Spherical proliferation may be accompanied by slight encapsulation. Compression of surrounding liver parenchyma often occurs. Normal lobular architecture usually present but may be distorted. Portal triads and central veins may be present. Bile duct and oval cell proliferation may be present. Hepatocytes appear slightly altered, but may have slightly basophilic cytoplasm or prominent nucleoli. Increased mitotic index may be observed. Evidence of prior or ongoing hepatocellular damage, such as apoptosis/necrosis, chronic inflammation, chronic congestion, fibrosis, cirrhosis, or a known cause of toxicity. Lesions in rats tend to be more nodular than in mice.
174. Non-Regenerative Hyperplasia mals. Some pathologists regard vacuolated foci as focal fatty change and do not consider them a subtype of focus of cellular alteration. Hyperplasia, Hepatocellular, Non-Regenerative (Figures 109 and 110) Synonyms: Hyperplasia, hepatocellular, focal hepatocellular hyperplasia. Pathogenesis: A spontaneous or treatment-associated prolif- erative collection of hepatocytes spanning several lobules and without evidence of prior hepatic damage. Diagnostic features: A relatively large lesion that is often greater than sev- eral adjacent lobules and is occasionally accompa- nied by angiectasis and/or spongiosis hepatis (cystic degeneration). Comprised of slightly enlarged hepatocytes. Hepatocytes are tinctorially similar to surrounding parenchyma. The liver plates in the lesion tend to merge with the adjacent hepatic parenchyma. May be minimal to mild compression of adjacent hepatic parenchyma. Lobular architecture is maintained. Portal triads and central veins are present. When accompanied by angiectasis/spongiosis hepa- tis, hepatic cords may be distorted. Differential diagnosis: Focus of cellular alteration—phenotypical or tinctor- ial variation is present. Generally not associated with chronic liver damage, though foci of cellular alteration may occur in damaged liver. Adenoma, hepatocellular—loss of normal lobular architecture with irregular growth pattern. Liver plates often impinge perpendicular or obliquely on the sur- evidence of existing or prior hepatocellular injury. Diagnostic difficulties occur when preneoplastic foci and hepatocellular adenomas occur in the same liver sections of older rodents. This lesion may be similar to that of hepatic nodular hyperpla- sia in dogs. There are basically two variations of non-regenerative hepatocellular hyperplasia. One is relatively smaller and is accompanied by angiectasis and/or spongiosis hepatis and the other tends to be larger than several lobules. The former occurs in both sexes and the latter predominantly in untreated female control F344 rats but occasionally reported in treated rats (Tasaki et al. 2008; Hailey et al. 2005; Bach et al. 2010). When present near the capsular surface, this type of nodular hyperplasia may be evident grossly as a raised area. The proliferating cell nuclear antigen (PCNA) labeling index in these nodules is increased in comparison with surrounding parenchyma and the lesion is glutathione S-transferase pla- cental form (GSTP) immunonegative. Very early non-regenerative hyperplasia may be the size of small foci of cellular alteration and are identified by their altered growth pattern and tinctorial similarity to surrounding parenchyma (see Figure 109). Hyperplasia, Hepatocellular,Regenerative (Figures 111–113) Synonyms: Hyperplasia, hepatocellular; hyperplasia, regenera- tive; hyperplasia, nodular; regeneration, nodular. Pathogenesis: A nodular regenerative response to prior or con- tinuous hepatocellular damage. Diagnostic features: Focal or multifocal (nodular) appearance. Lesion may reach several millimeters in diameter. Spherical proliferation may be accompanied by slight encapsulation. Compression of surrounding liver parenchyma often occurs. Normal lobular architecture usually present but may
175. Toxicologic Pathology 38: 9-36 (2010) Non-Regenerative Hyperplasia
176. Kupffer Cell Hyperplasia/Hypertrophy no evidence of liver toxicity. Although this response is also hyperplasia (hepatocellular, regenerative), it is not to be con- fused with the nodular hepatic response to toxic damage to hepatocytes. After ninety-six hours, the liver may be almost normal histologically. In mice however, chronic biliary lesions may be seen in the liver after PH. Hypertrophy/Hyperplasia, Kupffer Cell (Figures 114 and 115) Synonyms: Kupffer cell proliferation; histiocytosis, focal or diffuse. Pathogenesis: Following phagocytosis of foreign material, estrogen treatment, inflammatory conditions, and response to cytokines. A rare spontaneous finding. Diagnostic features: Diffuse to multifocal proliferation of oval to spinde- loid cells lining sinusoids. Cells resemble histiocytes and often contain phago- cytic material. May form as sheets or nodules. Hypertrophy can occur without hyperplasia and vice versa. Pathogenesis: Proliferation of fat-storing perisinusoidal cells. Diagnostic features: Focal or diffuse proliferation of Ito cells. May grow in sheets, clusters, or along cords of hepatocytes. Cells vary in size and shape and are vacuolated. Multiple cytoplasmic fat droplets of different size occur. The nuclei are ovoid or round and may be indented by cytoplasmic lipid droplets. Modest amount of collagenous matrix may be present. Differential diagnosis: Fatty change/Lipidosis—the cytoplasm of fat cells may be clearer than that of Ito cells. Ito cell tumor—larger and more extensive than hyperplasia. Partially distinct compression of adja- cent hepatic parenchyma. Comment: Ito cell hyperplasia is extremely rare and occurs predominantly in mice. It arises from fat-storing perisinusoi- dal cells, better known as Ito cells (Dixon et al. 1994; Enzan 1985; Tillmann et al. 1997). The biological behavior of the at Society of Toxicologic Pathology on August 8, 2013tpx.sagepub.comDownloaded from
177. Kupffer Cell Hyperplasia
178. Kupffer Cell Hyperplasia
179. Ito Cell Hyperplasia plastic foci and hepatocellular adenomas occur in the same liver sections of older rodents or in livers with many induced foci and tumors. In livers with partial hepatectomy (PH), the pattern of hyperplasia at twenty-four to seventy-two hours post surgery is diffuse hepatocyte hyperplasia with many mitotic figures and no evidence of liver toxicity. Although this response is also hyperplasia (hepatocellular, regenerative), it is not to be con- fused with the nodular hepatic response to toxic damage to hepatocytes. After ninety-six hours, the liver may be almost normal histologically. In mice however, chronic biliary lesions may be seen in the liver after PH. Hypertrophy/Hyperplasia, Kupffer Cell (Figures 114 and 115) Synonyms: Kupffer cell proliferation; histiocytosis, focal or diffuse. Pathogenesis: Following phagocytosis of foreign material, estrogen treatment, inflammatory conditions, and response to cytokines. A rare spontaneous finding. Diagnostic features: Diffuse to multifocal proliferation of oval to spinde- loid cells lining sinusoids. Cells resemble histiocytes and often contain phago- cytic material. May form as sheets or nodules. Hypertrophy can occur without hyperplasia and vice versa. Hyperplasia, Ito Cell (Figures 116–118) Synonyms: Stellate cell; perisinusoidal cell; fat-storing perisi- nusoidal cell. Pathogenesis: Proliferation of fat-storing perisinusoidal cells. Diagnostic features: Focal or diffuse proliferation of Ito cells. May grow in sheets, clusters, or along cords of hepatocytes. Cells vary in size and shape and are vacuolated. Multiple cytoplasmic fat droplets of different size occur. The nuclei are ovoid or round and may be indented by cytoplasmic lipid droplets. Modest amount of collagenous matrix may be present. Differential diagnosis: Fatty change/Lipidosis—the cytoplasm of fat cells may be clearer than that of Ito cells. Ito cell tumor—larger and more extensive than hyperplasia. Partially distinct compression of adja- cent hepatic parenchyma. Comment: Ito cell hyperplasia is extremely rare and occurs predominantly in mice. It arises from fat-storing perisinusoi- dal cells, better known as Ito cells (Dixon et al. 1994; Enzan 1985; Tillmann et al. 1997). The biological behavior of the at Society of Toxicologic Pathology on August 8, 2013tpx.sagepub.comDownloaded from
180. Bile Duct Hyperplasia lesion is not well established. There appears to be a continuum with Ito cell tumor (see the following), which may be just an exaggerated and sometimes more localized form of Ito cell hyperplasia. Bile Duct Hyperplasia (Figures 119–122) Pathogenesis: A spontaneous change in portal areas of older animals; may be induced or exacerbated by treatment. Diagnostic feature: Increased number of small bile ducts arising in portal region. May not involve all portal areas. May be associated with periductular fibrosis and periductular cell infiltration. Biliary epithelium is well differentiated, forming normal ducts. Biliary epithelium may show degenerative or atrophic changes. May be associated with oval cell hyperplasia. May contain mucous metaplasia or hyalinosis in specific situations in mice. Cystic form. Focal bile duct proliferation with cystic dilation of ducts may occur. Usually acini lined by flattened epithelium. Differential diagnosis: Diagnostic features: Consists of dilated to cystic bile ducts filled with mucus and cellular debris and surrounded by inflammatory cell infiltrates and connective tissue. Glandular epithelium is typically a single layer and varies from flattened to tall columnar hyperbasophi- lic and pleomorphic cells along with goblet cells and occasional Paneth cells. Glandular epithelium, particularly in cystic glands, may be partially lost through degeneration resulting in crescent shaped structures. Central portions of large lesions may become sclero- tic with only remnants of biliary epithelium suggest- ing regression. Lesions may be limited to small foci but may occupy large interconnecting areas of a lobe without mark- edly disturbing the lobe outline. Lesion growth typically involves contraction with retraction of surrounding parenchyma. Markedly dilated or cystic mucus-filled glands along the liver capsule may protrude above the lobe outline. Older lesions may be shrunken from the liver surface and appear as scars. Regenerative hepatocellular hyperplasia may be present when there is extensive parenchymal involvement.
181. Bile Duct Hyperplasia
182. Excessive Bile Duct Hyperplasia Exacerbated by Treatment
183. Bile Duct Hyperplasia and Inflammation Treated Female Sprague Dawley Rat Tx: PCB118 Dx: Bile duct hyperplasia
184. Treated Female Sprague Dawley Rat Tx: PCB118 Dx: Bile duct hyperplasia
185. Bile duct hyperplasia is a common aging change in rodents may be accompanied by chronic inflammaDon Vehicle Female F344 Rat Study: Beta Thujone Dx: Bile duct hyperplasia
186. Sprague Dawley Female High-dose Tx: TCDD Dx: Bile duct fibrosis
187. Mdr2 Mouse
188. Mdr2 Mouse
189. Mdr2 Mouse
190. Oval Cell Hyperplasia features (Bannasch and Zerban, 1990; Sirica 1992), unequivo- cal metastases have not been confirmed in most cases. This lesion is not observed in humans. Oval Cell Hyperplasia (Figures 127–129) Synonyms: Oval cell proliferation; bile ductule cell hyperplasia. Pathogenesis: Arises from terminal ductule epithelial cells (canal of Hering cells) spontaneously, following liver infec- tions, and secondary to hepatotoxic injury. Diagnostic features: Generally originates from portal areas and is often multifocal. Consists of a single or double row of oval to round cells along sinusoids in linear arrays. May form a few or many small ductules with stream- ing into the hepatic parenchyma. Formation of incomplete duct-like structures may be present. Cells are usually uniform in size and shape and may be fusiform. Cells have scant pale basophilic cytoplasm and round or oval nuclei. Oval cells express keratin. Differential diagnosis: G. Neoplasms Introduction The rodent liver is the most common target site of chemical carcinogens (Maronpot et al. 1986; Evans and Lake 1998), per- haps due to its major function as a metabolizing and detoxifying organ for xenobiotics. Rodent hepatocarcinogens are usually hepatotoxins. The chronic toxicity of these toxins may contribute to hepatocarcinogenesis although genotoxic liver carcinogens are often also hepatotoxins. There is over a thirty- year history of experimental induction (Frith and Wiley 1982; Malarkey et al. 1995; Evans et al. 1992; Ward et al. 1983, 1986; Ward, Lynch, and Riggs 1988; Popp 1984) and classifica- tion of preneoplastic and neoplastic lesions of the rat and mouse liver in book chapters (Bannasch and Zerban 1990; Brooks and Roe 1985; Greaves and Faccini 1984; Jones and Butler 1978; Ward 1981; Harada et al. 1999; Eustis et al. 1990) and by committee (ILAR 1980) or toxicologic pathology societies (Standardized System of Nomenclature and Diagnos- tic Criteria
[SSNDC] Guides, http://www.toxpath.org/ ssndc.asp). Terminology has evolved to the present nomencla- ture that is also based on many publications on liver carcinogenesis. There is evidence from experimental studies documenting the regression of proliferative hepatocellular lesions including foci of cellular alteration, hepatocellular adenomas, and hepato-
191. Oval Cell Hyperplasia Treated Female Sprague Dawley Tx: PCB Mixture Dx: Oval cell proliferation
192. Oval Cell Hyperplasia Treated Female Sprague Dawley Tx: PCB Mixture Dx: Oval cell proliferation
193. Cholangiofibrosis nuum ust an o cell older tal nd ng or in of Diagnostic features: Consists of dilated to cystic bile ducts filled with mucus and cellular debris and surrounded by inflammatory cell infiltrates and connective tissue. Glandular epithelium is typically a single layer and varies from flattened to tall columnar hyperbasophi- lic and pleomorphic cells along with goblet cells and occasional Paneth cells. Glandular epithelium, particularly in cystic glands, may be partially lost through degeneration resulting in crescent shaped structures. Central portions of large lesions may become sclero- tic with only remnants of biliary epithelium suggest- ing regression. Lesions may be limited to small foci but may occupy large interconnecting areas of a lobe without mark- edly disturbing the lobe outline. Lesion growth typically involves contraction with retraction of surrounding parenchyma. Markedly dilated or cystic mucus-filled glands along the liver capsule may protrude above the lobe outline. Older lesions may be shrunken from the liver surface and appear as scars. Regenerative hepatocellular hyperplasia may be present when there is extensive parenchymal involvement. HE HEPATOBILIARY SYSTEM 31S
194. Cholangiofibrosis Female Sprague Dawley Treated Tx: PCB Mixture Ki-67 Immunopositivity
195. Cholangiofibrosis Treated Female Sprague Dawley Tx: PCB Mixture Dx: Bile duct hyperplasia
196. Cholangiofibrosis Treated Female Sprague Dawley Tx: PCB Mixture Dx: Cholangiofibrosis
197. Cholangiofibrosis
198. Cholangiofibrosis Treated Female Sprague Dawley Tx: PCB Mixture Dx: Cholangiofibrosis
199. Cholangiofibrosis Has been called intestinal metaplasia
200. Cholangiofibrosis Male F344 Treated Rat Tx: Estragole subchronic study Dx: Cholangiofibrosis
201. Cholangiofibrosis
202. Cholangiofibrosis vs. Cholangiocarcinoma
203. Gallbladder
204. Normal Gallbladder
205. Normal Gallbladder
206. Normal Gallbladder
207. Normal Gallbladder
208. Submucosal Edema
209. Submucosal Edema
210. Inflammation Cytoplasmic Alteration
211. Inflammation Cytoplasmic Alteration
212. Cholecystitis
213. Cholecystitis
214. Cholecystitis
215. Cholecystitis
216. Epithelial Hyperplasia
217. Epithelial Hyperplasia
218. Epithelial Hyperplasia
219. Epithelial Hyperplasia
220. Epithelial Hyperplasis vs. Papilloma
221. Epithelial Hyperplasis vs. Papilloma ?
222. Some Liver Artifacts
223. Hematoxylin Crystals (Need to filter the hematoxylin)
224. Another Example
225. Multiple Surface Nodules
226. Cytoplasmic Vacuoles
227. Cytoplasmic Vacuoles
228. •  Rats remained in CO2 chamber •  after death for a few minutes •  Time-dependent postmortem change •  A result of plasma influx •  Associated with congestion and •  increased liver weight •  Males more sensitive than females
229. Large Clear Vacuoles (Some Small Vacuoles are in Hepatocytes)
230. TOXICOLOGY AND APPLIED PHARMACOLOGY 36,31-39 (1976) Hepatocyte Vacuolation and Increased Liver Weight Occurring in Anoxic Rats’ BARBARA I. SYKES,ELIZABETH PENNY AND I. F. H. PURCHASE Central Toxicology Laboratories, Itnperial Chemical Industries Limited, Alderley Park, Cheshire SKI0 4TJ, England Received May 14, 1975, accepted December 2,1975 Hepatocyte Vacuolation and IncreasedLiver Weight Occurring in Anoxic Rats.SYKES, BARBARA I., PENNY, ELIZABETH AND PURCHASE, I. F. H. (1976). Toxicol. Appl. Pharmacol. 36, 31-39. Hepatocyte vacuolesare often observedhistologically in rats usedin toxicology tests.They are regular in outline, contain eosinophilicmaterial, and severalmay be presentin individual hepatocytes,particularly thosein the centrilobular areas.This vacuolationhasbeenshownto resultfrom anoxia.It occursin ratsthat arenot bledimmediatelyafter deathandif thereisaslightdelayof only afewminutesbeforeremovalof theliver. It isenhancedif theanimals arekilled usingvolatileanestheticsinanoxic conditions.Thevaculoescon- tain bloodplasmawhichisthought to movethroughthedisruptedspacesof Disseandhepatocyteplasmamembranesinto thecells.Anoxic vacuolation isassociatedwith anincreaseinliver weight.It isimportant, therefore,both from a morphologicalviewpoint andwith regardto the liver/body weight ratio, that this lesionbeavoided in toxicology testsby ensuringthat the necropsyis performedand that the animalsare bled immediatelyafter cessationof breathing. At thetermination of toxicology studiesin ratscarried out in our laboratory, the animals are killed with halothane vapor in a closedjar. The amount of anesthetic, the composi- tion of the air in thejar, and the time during which the rats are left either in the jar or on the bench before postmortem examination, may vary considerably. It was observed by light microscopy that in someratsfrom thesestudiestherewasextensivevacuolation of liver cellsandcorresponding ultrastructural changes.Vacuolesof various sizes,up to 15pm in diameter, weredistributed throughout the cytoplasm of somehepatocytesand the sinusoidal areawas disrupted. In a report on “watery vacuolation of liver cells,” Trowel1 (1946)describedasimilar change.He indicated that two factors werenecessaryfor vacuolation to occur: (1) liver anoxia; and(2) intrasinusoidal pressuremustbemaintained at leastat its normal value; if it is greater, vacuolation is enhanced.He distinguishedbetween irzuiuo vacuolation due to severe anoxia and postmortem vacuolation in the highly anoxic liver after cessationof breathing which arisesif the animal is not bled promptly. As preliminary inquiries showed that there may be an association between the occurrence of vacuolation and the time the animals areleft in the killing jar, an investi- gation into postmortem conditions which gave rise to this lesion was initiated. The study wasthen extended to include other volatile anestheticsusedin similar conditions, 1Addressreprintrequestsandcorrespondenceto I. F. H. Purchase. Copyright 0 1976 by Academic Press, Inc. 31 •  Anoxic vacuoles •  Animals not bled immediately •  aer death •  Liver not removed promptly •  Associated with increased •  liver weight •  Blood plasma moves through •  disrupted space of Disse and •  hepatocyte membranes