Hepatocyte Specific Antigen (HepPar1, Hep paraffin 1, OCH1E5) is an antigen expressed in hepatocyte mitochondria. In immunohistochemistry, it is considered a sensitive marker for differentiating hepatocellular carcinomas (HCC) from other cancers such as cholangiocarcinomas. It may also be a useful biomarker for characterizing metaplasia in the intestine and early Barrett esophagus. Hepatocyte Specific Antigen is also found in some gastric adenocarcinomas as well as in a few other non-hepatic tumors. In normal tissue, it has granular cytoplasmic positivity in hepatocytes and small intestine epithelium. References: Mod Pathol. 2003 Feb;16(2):137-44, PMID: 12591966; Am J Clin Pathol 2012;137:111, PMID: 22180484; Malays J Pathol 2006;28:87, PMID: 18376797