Distribution of cytokeratin 19-positive biliary cells in cirrhotic nodules, hepatic borderline nodules (atypical adenomatous hyperplasia), and small hepatocellular carcinomas.

Borderline nodule (BN) in the cirrhotic liver is considered to be a precancerous lesion leading to hepatocellular carcinoma (HCC). We investigated the distribution of cytokeratin 19 (CK 19)-positive biliary cells, recognizable by a monoclonal antibody AE1, in normal livers, chronic active hepatitis, cirrhosis, BN, and small HCC. The CK 19-positive biliary cells in the hepatic parenchyma were clearly divisible into two types (I and II). Type I cells were located within the hepatic parenchyma as small clusters forming small tubules (intraparenchymal ductules). Type II cells were bile ductules located in the peripheral rim of the hepatic lobules or hepatocellular lesions (peripheral ductular reaction) and were continuous with proliferated bile ductules in fibrous septae or portal tracts. In chronic active hepatitis and regenerative nodules of cirrhosis, a few type I cells and a variable number of type II cells were present. In the BN, all cases harbored a few type I cells as well as a variable number of type II cells. The type II cells in the BN were fewer in number and more randomly distributed than those in chronic active hepatitis and cirrhosis. Malignant foci in some BNs lacked CK 19-positive biliary cells. In small HCC, no CK 19-positive biliary cells were found; instead, AE1-positive HCC cells were present in three cases (17%). Although a great majority of type I cells corresponded to intraparenchymal ductules, some type I cells in the BN were composed of rather large tubules considered as interlobular bile ducts.(ABSTRACT TRUNCATED AT 250 WORDS)