[Mediastinal teratoma in a newborn infant].

A newborn with mediastinal teratoma developed tachypnea and cyanosis within the first hours of life. Chest x-ray revealed a subtotal opacification of the left hemithorax, which at first was suspected to be caused by a cardiomegaly. Ultrasound examination demonstrated a large mass in the left hemithorax with multiple echo-free areas. This finding was suspicious for a mediastinal teratoma. The tumor which was originating from the mediastinum was apple-sized and could be resected totally by thoracotomy. Histology revealed a cystic teratoma covered with normal thymus tissue.