Leydig-cell tumor of the testis with gynecomastia and elevated estrogen levels.

A normally-virilized 24-year-old white man who had gynecomastia was found to have a Leydig-cell tumor of the testis, without demonstrable metastases. Hormonal evaluation revealed negative serum and urine tests for human chorionic gonadotropin, and normal steroid excretion. Prior to orchiectomy, serum estradiol was elevated and serum testosterone depressed; postoperatively these values reverted to normal. Attempts to quantitative the estradiol content of the tumor failed to show a significant increase over normal testicular tissue, however. Histologically, the tumor showed classic Reinke crystalloids, the nature of which remains undefined. Electron-microscopic studies showed these crystals to have a regular hexagonal pattern.