Klinefelter's syndrome associated with testicular microlithiasis and mediastinal germ-cell neoplasm.

Klinefelter's syndrome is a genetic disorder of male sexual differentiation characterized by an XXY karyotype. Although considered a benign condition, it is associated with several types of malignancies, including mediastinal germ-cell neoplasm. In addition, Klinefelter's syndrome has been rarely associated with testicular microlithiasis. Whereas patients with Klinefelter's syndrome have an increased incidence of extragonadal germ-cell neoplasms, patients with testicular microlithiasis have a predisposition to testicular germ-cell neoplasms. To our knowledge, an extragonadal germ-cell neoplasm has not been previously described in association with testicular microlithiasis. We present a patient with 2 unusual conditions, both of which are independently associated with Klinefelter's syndrome: mediastinal germ-cell neoplasm and testicular microlithiasis.