Two Cases of Rare Hepatocellular Nodular Lesion Caused by Circulatory Disturbance in Rat Livers

Abstract

Two cases of focal nodular lesions different from regenerative nodules or preneoplasia were found in rat livers. The lesion in Case No. 1 was found in the medial lobe and showed lobular structures with hypertrophic hepatocytes at the center of the lobular structures and atrophic hepatocytes at the periphery. It contained the portal veins but very few bile ducts and hepatic arteries in the central areas. This nodule was diagnosed as nodular regenerative hyperplasia based on its histopathological similarities to such lesions in human cases. The lesion in Case No. 2 was found in the caudate lobe, and contained a large sclerosing portal vein with preserved normal portal triads accompanied by degenerative cellular and inflammatory changes. Based on its histopathological similarities with such lesions in aged canines, this lesion was diagnosed as nodular hyperplasia. Observed vascular abnormalities in both these cases suggested the presence of previous circulatory disturbance with a close anatomical association to the hyperplastic lesions. We, thus, propose a new histopathological entity of hepatocellular hyperplasia which develops in association with local circulatory disturbance and is distinct from post-necrotic regenerative hyperplasia. (J Toxicol Pathol 2007; 20: 167-173)