Abstract
The final version of the international harmonized nomenclature for proliferative lesions in rats was issued on June 21, 2000. The recommended nomenclature for proliferative lesions in the liver includes focus of cellular alteration, regenerative hepatocellular hyperplasia, cholangiofibrosis, cholangiofibroma, oval cell hyperplasia, hepatocellular adenoma, hepatocellular carcinoma, bile duct hyperplasia, cholangioma, cholangiocarcinoma, hepatocholangiocellular adenoma, and hepatocholangiocellular carcinoma. Foci of cellular alteration are further classified into the following phenotypes: amphophilic, diffusely basophilic, tigroid basophilic, clear cell, eosinophilic, and mixed (basophilic/eosinophilic). Hepatocellular carcinomas are divided into 3 types based on their growth patterns: acinar, solid, and trabecular. In consideration of this international harmonized nomenclature, the current classification, terminology, and diagnostic criteria for prolifrative lesions in the liver of rats recommended by the Japanese Society of Toxicologic Pathology (JSTP) were reviewed by a Working Group of the JSTP. The hepatic proliferative lesions reviewed by the present Working Group included lesions of hepatocellular, cholangiocellular, mixed hepatocholangiocellular, sinusoidal, and hemangioendothelial origins. Any comments and questions on these lesions were discussed among pathologists in the Working Group and the results of discussions were presented at the 1st seminar on the continuing education program of the JSTP in November 2000.
