Leydig cell clusters in the adult human testis are known to enlarge during chronic stimulation with excess LH as in Klinefelter's syndrome or following administration of exogenous human chorionic gonadotropin (hCG). However, the ultrastructural features of this hyperplasia, to our knowledge, have not been reported in association with testicular neoplasms producing hCG.We report the case of a 21-year-old man who sought medical attention because of gynecomastia. Laboratory investigation revealed a marked increase in serum hCG and elevated a-fetoprotein. A testicular mass was palpable on examination and the patient underwent orchiectomy.
