[Mediastinal teratocarcinoma and hypophyseal stalk germinoma in a patient with Klinefelter syndrome].

A 8 1/2 year old boy is reported, who was admitted because of rapid growth and premature development of pubic hair. Pseudopubertas praecox was diagnosed, caused by a beta-HCG producing mediastinal teratocarcinoma. The patient also had a pituitary germinoma. His karyotype was 47, XXY. While the association of Klinefelter's syndrome and breast cancer is well known, only recently an increased incidence of mediastinal germ cell tumors in this syndrome has been established, which again is demonstrated in this case report.