Hepatocyte paraffin 1 antibody does not distinguish primary ovarian tumors with hepatoid differentiation from metastatic hepatocellular carcinoma.

Anti-hepatocyte antibody, hepatocyte paraffin 1, is a monoclonal antibody that is highly specific for normal and neoplastic hepatocytes and that can differentiate hepatocytic from nonhepatocytic tumors. This marker has been rarely studied in extra-hepatic tumors and to our knowledge has not been investigated in ovarian tumors with hepatoid differentiation. We studied hepatocyte paraffin 1 immunoreactivity in a series of ovarian hepatoid carcinomas, ovarian hepatoid yolk sac tumors (YSTs), and hepatocellular carcinomas metastatic to the ovary to assess the potential utility of hepatocyte paraffin 1 in differential diagnosis. Hepatocyte paraffin 1 positivity was seen in three of seven ovarian hepatoid carcinomas, five of eight hepatoid yolk sac tumors, and six of eight metastatic hepatocellular carcinomas. The extent of positivity ranged from <25% to >50% of the tumor cells. There was strong coarsely granular cytoplasmic staining in all three tumor types without a distinctive staining pattern in any group. The degree of hepatic differentiation correlated with hepatocyte paraffin 1 positivity in the three groups: 83% of the well differentiated tumors, 50% of the moderately differentiated tumors, and none of the poorly differentiated tumors were positive. All ovarian hepatoid carcinomas were either immunoreactive for alpha-fetoprotein or had an elevated serum alpha-fetoprotein level; more than half of these tumors were hepatocyte paraffin 1 negative. All but one hepatocyte paraffin 1 negative hepatoid yolk sac tumor and ovarian hepatocellular carcinoma were also negative for alpha-fetoprotein. In conclusion, hepatocyte paraffin 1 is positive in primary ovarian tumors with hepatoid differentiation, with the degree of hepatocyte paraffin 1 positivity correlating with the degree of hepatoid differentiation. Hepatocyte paraffin 1, however, is not useful in distinguishing metastatic hepatocellular carcinoma from primary ovarian hepatoid carcinoma or hepatoid yolk sac tumor.