Hepatocyte specific antigen is useful in studying hepatocellular tumors. It may be useful in differentiating clear cell hepatocellular carcinomas from other clear cell malignancies. It has been shown in the literature to be useful in differentiating hepatoblastoma of embryonal type from small round cell tumors of childhood. Hepatcoyte labels an antigen in the mitochondrial fraction of the liver homogenates. Hepatoblastoma is the most common primary tumor of the liver in children. The use of specific hepatocyte markers and also of alpha Fetoprotein or carcinoembryonic antigen are useful for the identification of normal and malignant fetal hepatocytes. HSA (Hepatocyte Specific Antigen) has been demonstrated consistently in the vast majority of hepatocellular carcinomas. Studies have shown the utility of HSA in the differential diagnosis of hepatocellular carcinoma, cholangiocarcinoma and hepatoblastomas.