The significance of alpha-fetoprotein and other tumour markers in differential immunocytochemistry of primary liver tumours.

One hundred benign and malignant primary liver tumours were screened immunocytochemically for alpha-fetoprotein (AFP), alpha 1-antitrypsin, alpha-human chorionic gonadotropin, carcinoembryonic antigen (CEA), keratin and vimentin. Alpha-fetoprotein was found in 16/63 (24%) hepatocellular carcinomas and in two hepatoblastomas. When comparing tissue positivity for AFP with tumour differentiation, grade 1 hepatocellular carcinomas were found to be negative, while 21% of grade 2, 36% of grade 3 and 16% of grade 4, respectively, stained positively. Alpha-fetoprotein positive cells were present in 9/10 hepatocellular carcinomas with serum levels exceeding 5000 ng/ml, but were absent in 17 tumours with serum AFP levels below 5000 ng/ml. All tumours other than hepatocellular carcinomas and hepatoblastomas were AFP negative. Carcinoembryonic antigen was present in 72% of cholangiocarcinomas, but was demonstrated in only one hepatocellular carcinoma. This exception was a combined hepatocellular-cholangiocarcinoma in which CEA expression was restricted to the cholangiocellular part. Alpha 1-antitrypsin was found in 4/63 hepatocellular carcinomas, in 2/2 fibrolamellar carcinomas and in 2/18 cholangiocarcinomas. Alpha-human chorionic gonadotropin was detected in one hepatocellular carcinoma and was strongly expressed in both fibrolamellar carcinomas. Weak staining for keratin was seen in most tumours with hepatocellular differentiation. All cholangiocarcinomas, in contrast, were strongly labelled with the keratin antibody. Co-expression of keratin and vimentin was observed in seven poorly differentiated hepatocellular carcinomas and three cholangiocarcinomas as well as in the two hepatoblastomas. The findings suggest that AFP is a diagnostic but rather insensitive immunocytochemical marker for hepatocellular differentiation in malignant liver tumours; CEA and keratin may help in discriminating cholangiocarcinomas from hepatocellular carcinomas.