Immunoreactivity of Hep Par 1 in hepatic and extrahepatic tumors and its correlation with albumin in situ hybridization in hepatocellular carcinoma.

We evaluated the expression of Hep Par 1 (hepatocyte paraffin 1 monoclonal antibody) in 42 hepatocellular carcinomas (HCCs), 25 cholangiocarcinomas, 18 tumors metastatic to the liver, and 87 primary extrahepatic tumors. Albumin in situ hybridization (ISH) was performed in the HCC cases. Of 42 cases of HCC, 39 (93%) were positive for Hep Par 1. All cases of cholangiocarcinoma, renal cell carcinoma, adrenocortical carcinoma, and islet cell tumors were negative; 1 case each of primary urinary bladder (n = 10) and pancreatic (n = 10) adenocarcinoma and 3 of 11 cases of primary pulmonary adenocarcinoma showed focal positivity; 7 of 10 gastric and 6 of 8 esophageal adenocarcinomas were strongly positive. Albumin ISH was positive in 39 (93%) HCC cases. All cases of HCC were positive for Hep Par 1 or albumin ISH. Hep Par 1 immunoreactivity has high sensitivity in the diagnosis of HCC. Strong positive staining also occurs in gastroesophageal adenocarcinomas. Cholangiocarcinoma and carcinomas from most other sites are negative for Hep Par 1. Hep Par 1 immunoreactivity shows high correlation with albumin ISH; their combined use for diagnosis of HCC had a sensitivity of 100% in this population.