An immunohistochemical study of hepatic atypical adenomatous hyperplasia, hepatocellular carcinoma, and cholangiocarcinoma with alpha-fetoprotein, carcinoembryonic antigen, CA19-9, epithelial membrane antigen, and cytokeratins 18 and 19.

Eight hepatic atypical adenomatous hyperplasias (AH), 30 hepatocellular carcinomas (HCC) consisting of 11 well-, 13 moderately and six poorly differentiated HCC, and 10 intrahepatic cholangiocarcinomas (CC) were investigated immunohistochemically with anti-alpha-fetoprotein (AFP), carcinoembryonic antigen (CEA), CA19-9, epithelial membrane antigen (EMA), and cytokeratins (CK) 18 and 19 antibodies. Immunostaining was regarded as positive when more than 5% of cells were stained. Alpha-fetoprotein was positive, although focally, in five (17%) of 30 HCC but negative in all AH and CC. Carcinoembryonic antigen (polyclonal antibody) did not stain the cytoplasm of all AH and HCC, but stained two (25%) of eight AH and 10 (33%) of 30 HCC in a bile canalicular staining manner. Carcinoembryonic antigen showed intracytoplasmic or luminal border staining in six (60%) of 10 CC. CA19-9 was negative in all AH and HCC, while six (60%) of 10 CC were positive for CA19-9. Epithelial membrane antigen was positive in one (13%) of eight AH, seven (23%) of 30 HCC and in all 10 cases of CC. Cytokeratin 18 was positive in all AH, HCC and CC. Cytokeratin 19 was negative in both AH and HCC, whereas it stained the cytoplasm of tumor cells in all CC diffusely and intensely. These results suggest that immunostaining of AFP, CEA, CA19-9, EMA, CK18 and CK19 are not useful in the differential diagnosis between AH and well-differentiated HCC, and that CK19 is the most suitable reagent for the differential diagnosis between HCC and CC.