The distinction between cholangiocarcinoma, hepatocellular carcinoma and liver metastasis is important but at times difficult solely on microscopic appearances. The Das-1 immunostain exhibits specificity for colonic epithelium. However, its staining of cholangiocarcinomas and hepatocellular carcinomas has not been extensively studied. We evaluated the staining properties of the Das-1 immunostain in cholangiocarcinoma and hepatocellular carcinoma. Forty-four cholangiocarcinomas, 16 hepatocellular carcinomas, 17 colon adenocarcinomas metastatic to the liver and 3 benign biliary tumors were studied. The cases were stained with the Das-1 antibody following deparaffinization and rehydration. The slides were evaluated for membranous and/or cytoplasmic staining in a blinded fashion. The percentage of tumor cells exhibiting strong staining was estimated. Of the intra-hepatic cholangiocarcinomas, 4 of 36 (11%) and 2 of 16 (13%) hepatocellular carcinomas were positive for Das-1, though typically only in rare cells. In comparison, 7 of 8 (88%) extra-hepatic cholangiocarcinomas, 13 of 17 (77%) of metastatic colon carcinomas and 3 of 3 (100%) benign tumors of the biliary tract were strongly positive in a diffuse pattern. The Das-1 immunostain may play a useful role in evaluating liver malignancies.

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