Virilizing stromal Leydig cell tumor (Leydig cell-containing thecoma) of the ovary in pregnancy. A case report with extensive immunohistochemical investigation of the tumor cells.

The rare case of a stromal Leydig cell tumor of the ovary occurring in a 21-year-old woman who developed signs of virilization during pregnancy is reported. Serum androgen levels were markedly elevated. At cesarean section, a slightly hypotrophic, but otherwise normal, female infant was delivered and a tumor of the right ovary measuring 12 cm in maximum diameter was resected. Histologic examination revealed a sex cord-stromal tumor consisting of spindle-shaped, thecomatous cells and a large number of loosely scattered clusters of large polygonal cells with abundant eosinophilic cytoplasm. Both types of tumor cells were strongly immunoreactive for vimentin, but exhibited no proliferative activity and no overexpression of p53 protein. A few of the polygonal cells contained typical crystalloids of Reinke. Cellular atypia was not a prominent feature, and a diagnosis of benign stromal Leydig cell tumor was established. As expected, 20 months after diagnosis the patient exhibits no signs of recurrence or dissemination. To the best of our knowledge this is only the second case of a stromal Leydig cell tumor occurring in pregnancy to be described.