Klinefelter's syndrome associated with mediastinal germ cell neoplasms.

Several case reports have suggested an association of primary mediastinal germ cell tumor (PMGCT) and Klinefelter's syndrome (KS). In an effort to confirm this association, 22 patients with mediastinal germ cell tumors had chromosome studies performed in a prospective fashion. Five patients (22%) had karyotypic or pathologic evidence of KS. All of the patients with KS had germ cell tumors of the nonseminomatous subtype and were relatively young (median age, 15 years). The literature confirms the findings of a young median age (18 years), nonseminomatous subtype, and mediastinal location of the germ cell neoplasm. We conclude that patients with KS are predisposed to the development of mediastinal nonseminomatous germ cell cancers.