Keratin polypeptides in malignant epithelial liver tumors. Differential diagnostic and histogenetic aspects.

Five monoclonal antibodies recognizing different keratin polypeptides in immunoblotting or different epithelial cell types in complex tissues were studied for their suitability as reagents for the differential diagnosis of primary and secondary malignant epithelial liver tumors. The broad specificity keratin antibodies lu-5 and KL-1 stained all epithelial liver neoplasms. In contrast the antibodies CK-7 (Ker-7-specific), CK-2 (Ker-18-specific) and KA-4 (Ker-19-specific in liver) allow these neoplasms to be divided into three groups: Hepatocellular carcinomas were CK-2-positive and CK-7-negative. Cholangiocellular carcinomas, liver metastases of extrahepatic bile duct carcinomas, liver metastases of a ductal carcinoma of breast, and a follicular thyroid carcinoma were stained positively by CK-2, CK-7, and KA-4. In 1 of 6 hepatocellular carcinomas neoplastic hepatocytes were focally labeled by KA-4. In a focal nodular hyperplasia of the liver modified hepatocytes were decorated not only by CK-2 but also by CK-7 and KA-4. Liver metastases of colorectal adenocarcinomas and of a carcinoid tumor were stained positively by CK-2 and KA-4 but not by CK-7.