[Klinefelter's syndrome associated with primary mediastinal germinal cell tumor].

A case of a man aged 25 year with Klinefelter's syndrome (KS) associated with a primary malignant germinal cell tumour is presented. Echocardiography was of assistance in the diagnosis as a tumour behind the heart was demonstrated. If patients with KS develop cardiopulmonary symptoms, referral for x-ray of the thorax is recommended. If there is enlargement of the heart or increase in width of the mediastinum, echocardiography should be performed. This case history emphasizes further that a negative cytological test does not disprove malignancy.