Granulosa cell tumor of the ovary with diffuse true hepatic differentiation simulating stromal luteinization

A case of granulosa cell tumor of the ovary associated with hepatocytic differentiation is reported in a 45-year-old patient with a torsioned ovarian tumor. Serum alpha-fetoprotein (AFP) levels were normal 6 days postoperatively. Histopathologically, the granulosa cell tumor was typically trabecular. Its cells had nuclear grooves and were positive only for vimentin. Scattered diffusely throughout the tumor were small groups of regular polygonal cells, the cytoplasm of which secreted bile and was strongly positive for keratin, carcinoembryonic antigen (CEA), alpha-1-antitrypsin (A1AT), and ferritin and moderately positive for fibrinogen and ceruloplasmin. These results unequivocally identified them as hepatic cells. The AFP negativity of the hepatic cells was interpreted as a sign of terminal hepatocytic differentiation. The scattered arrangement of the hepatocytes simulated stromal luteinization. As neither a primary liver tumor nor any associated germ cell tumor was found, the histogenesis of the hepatic cells was thought to be metaplastic.