Seminoma of the testis in a patient with 48,XXYY variant of Klinefelter's syndrome.

We believe this is the first reported case of seminoma in a patient with the 48,XXYY variant form of Klinefelter's syndrome. Moreover, the seminoma in this patient occurred in a normally descended testis. We report this case because patients with 48,XXYY Klinefelter's syndrome are often confined to institutions, where the diagnosis of testicular tumor may not be recognized as readily.