Mitochondrial membrane protein of unknown function almost exclusively occurring in liver cells, detected immunohistochemically with the mAb Hepatocyte Paraffin 1 (Hep Par 1, Clone: OCH1E5 or OCH1E5.2.10). The protein is also found in enterocytes (often focally) in small bowel mucosa.
The majority (70-90%) of primary hepatocellular carcinomas (HCC) are positive, sometimes only focally. Adenocarcinomas in the gastrointestinal (GI) tract has shown focal positivity in up to 50%. Also adenocarcinomas derived from pancreas, lung and ovary have occasionally shown positivity. Rare hepatoid adenocarcinomas of GI tract and other organs as well as hepatoid yolk sac tumour are positive.
Hepa is useful for the differential diagnosis of hepatocellular tumors in general, for the differentiation of clear cell HCC from other clear cell malignancies, and for the distinction of hepatoblastoma, especially the embryonal type, from other small, round-cell tumors of childhood. However, Hepa should be used in a panel, which in case of the differential diagnosis HCC should include, e.g., AFP, CD10, CD66a, CK7, CK20, and Glypican 3.
Liver can be used as positive control, in which virtually all liver cells must show an at least moderate granular cytoplasmic staining reaction. Tonsil can be used as negative control – no staining should be seen.
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