Superior vena caval syndrome in primary mediastinal germ cell tumors.

Upon examination, nine of 45 patients (20%) with primary mediastinal germ cell tumors were found to have superior vena caval syndrome. All patients were men (average age, 27). Superior vena caval syndrome was found with all mediastinal germ cell tumor cell types except mature teratoma. Primary mediastinal germ cell tumors should be strongly considered in the diagnosis of young men with a mediastinal mass and superior vena caval syndrome.