This presentations is focused on microscopic features of rat and mouse neoplastic liver lesions that are commonly seen during toxicologic pathology evaluation of rat and mouse two-year cancer bioassays.

Rodent Liver Neoplasia

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Index of Slides

1. Rodent Liver Lesions – Neoplastic R. R. Maronpot Photomicrographs courtesy of the National Toxicology Program (
2. Hepatocellular adenoma • Nodular and compressing • Oblique impingement on surrounding parenchyma • Loss of lobular structure • Difference in cell size and/or tinctorial staining • Occasional trapped portal triads
3. Hepatocellular tumor
4. Hepatocellular Adenoma
5. Hepatocellular Adenoma
6. Hepatocellular Adenoma
7. Hepatocellular carcinoma • Locally infiltrative • Cellular pleomorphism • Loss of normal lobular structure • Increased mitosis, necrosis, and/or hemorrhage may be present • Altered tinctorial staining • Variable growth patterns – Trabecular, acinar, solid, other
8. Hepatocellular tumor
9. Hepatocellular Carcinoma
10. Hepatocellular Carcinoma
11. Hepatocellular Carcinoma
12. Hepatocellular Carcinoma
13. Hepatocellular Carcinoma
14. Hepatocellular Carcinoma
15. Hepatocellular carcinoma
16. Carcinoma arising in Adenoma
17. Carcinoma Arising in Adenoma
18. Hepatoblastoma • Discrete nodular growth with variable structure, often within hepatocellular adenoma or carcinoma • Cells often small, strongly basophilic, and may be elongated • Cells arranged radially, concentrically, as rosettes, trabeculae and/or pseudoglands • Vascular cavities • Osteoid differentiation may be present
19. Hepatoblastoma arising in adenoma
20. Hepatoblastoma with Osseous Metaplasia
21. Cholangioma • Variable size and shape glandular acini • Expansive and compressive growth • Cells mostly in a single layer without surrounding stroma • Cells reasonably well differentiated with slightly basophilic cytoplasm • Simple and cytic forms • Occasional trapped hepatocytes
22. Cholangioma
23. Cholangioma
24. Cystic Cholangioma – Benign Bile Duct Tumor
25. Glandular structures lined by a single layer of cuboidal to columnar epithelium
26. Cystic Cholangioma
27. Cholangiocarcinoma • Locally invasive glandular, solid and/or papillary growth pattern • Cells are single or multiloayers with large nuclei and basophilic cytoplasm • May be associated with some fibrosis • A controversial version with intestinal metaplasia, extensive fibrosis, dilated mucus- and debris-filled glands, and inflammation is currently being debated
28. Cholangiocarcinoma
29. Cholangiocarcinoma
30. Well Differentiated Cholangiocarcinoma
31. Well-Differentiate Cholangiocarcinoma
32. Hepatocholangiocellular adenoma • Combines merged features of hepatocellular cords and single layered biliary ductules • Hepatocytes may form ductules that resemble biliary cells
33. Hepatocholangioma
34. Hepatocholangioma
35. Hepatocholangioma
36. Hepatocholangiocellular carcinoma • Features of hepatocellular carcinoma and/or cholangiocarcinoma • Cellular stratification and atypia of biliary component • Increased mitoses may be present
37. Hepatocholangiocarcinoma
38. Hepatocholangiocarcinoma
39. Hepatocholangiocarcinoma
40. Hepatocholangiocarcinoma
41. Hepatocholangiocellular carcinoma
42. Hepatocholangiocellular Carcinoma
43. Hepatocholangiocellular Carcinoma
44. Hepatocholangiocellular Carcinoma
45. Hepatocholangiocellular Carcinoma
46. Hepatocholangiocellular Carcinoma
47. Hepatocholangiocellular Carcinoma
48. Ito cell tumor • Focal to diffuse single or multicentric sheets and/or clusters of variably sized and shaped cells • Tumor cells often vacuolated and present along hepatocyte cords • Unencapsulated growth that replaces normal hepatic parenchyma • Spindle-shaped cells may be part of growth
49. Ito Cell Hyperplasia Ito Cell Tumor
50. Ito Cell Hyperplasia
51. Ito Cell Tumor
52. Ito Cell Tumor
53. Ito Cell Tumor
54. Ito Cell Tumor
55. Ito Cell “Tumor”
56. Ito Cell Tumor in a Rat
57. Ito Cell Tumor in a Rat
58. Histiocytic sarcoma • Single or multicentric nodules composed of uniform population of round to oval cells with foamy cytoplasm • Growth along sinusoids and vascular structures • Multinucleated giant cells may be present • Mitoses may be numerous
59. Histiocytic Sarcoma
60. Histiocytic Sarcoma
61. Histiocytic Sarcoma
62. Histiocytic Sarcoma
63. Histiocytic Sarcoma
64. Histiocytic Sarcoma
65. Histiocytic Sarcoma
66. Hemangioma • Blood-filled spaces lined by a single layer of uniform endothelial cells without atypia • Occasional solid areas of uniform endothelial cells without atypia may be present • May be multifocal and associated with angiectasis • Capillary and cavernous growth patterns are seen
67. Hemangioma
68. Hemangioma
69. Hemangioma
70. Hemangioma
71. Hemangiosarcoma • Pleomorphic multilayered and/or clustered pleomorphic endothelial cells • Various poorly formed and infiltrative vascular growth patterns • Undifferentiated areas and mitotic figures often present
72. Hemangiosarcoma
73. Hemangiosarcoma
74. Hemangiosarcoma
75. Hemangiosarcoma
76. Hemangiosarcoma
77. Lymphoma in a Tg Mouse
78. Lymphoma in a Tg.AC Mouse
79. Erythroleukemia in a Control Tg.AC Mouse
80. Erythroleukemia in a Control Tg.AC Mouse
81. Erythroleukemia in a TgAC Mouse
82. Erythroleukemia in a TgAC Mouse
83. Mononuclear Cell Leukemia
84. Mononuclear Cell Leukemia