Hepatoid variant of yolk sac tumor of the testis.

A case of testicular yolk sac tumor (endodermal sinus tumor) consisting predominantly of hepatoid cells is documented. A mass measuring approximately 4 x 3 cm was noted in the left testis of a 64-year-old man. Preoperative examination revealed an elevated serum level of alpha-fetoprotein (5479 ng/mL). Histologically, the lesion was composed predominantly of sheet-like or trabecular proliferation of hepatocyte-like cells with eosinophilic or clear cytoplasm. The tumor cells were immunoreactive for alpha-fetoprotein, antimitochondrial antibody, cytokeratin (AE1/AE3), alpha-1-antichymotrypsin, alpha-1-antitrypsin, albumin, carcinoembryonic antigen and epithelial membrane antigen. It was necessary to distinguish this variant lesion from metastatic hepatocellular carcinoma, embryonal carcinoma and hepatoid carcinoma.