Human focal nodular hyperplasia-like lesion in the liver of a cat.

A young cat clinically displaying marked ascites had multiple nodule hyperplasia in the liver. One of the nodules sampled at exploratory laparotomy was studied histopathologically. The nodule consisted mainly of hyperplastic hepatocytes with a central stellate scarlike connective tissue. The connective tissue had thick-walled blood vessels and radiating bands of fibrous connective tissue extending peripherally, dividing the nodule into pseudolobules. The lesions resembled focal nodular hyperplasia (FNH) in man. Serial section revealed a single large artery with the splitting of the internal elastic lamina running into the central connective tissue and branching to connect with the main vessels. The arterial branchings formed a spider-like structure. From these findings, it was suggested that the nodule had developed from a hepatic response to pre-existing vascular anomalies as had been reported in human FNH.