Primary mediastinal germ cell tumors. Histologic patterns of treatment failures at autopsy.

Twenty-five patients presented with primary mediastinal germ cell tumors at Roswell Park Memorial Institute between 1959 and 1984. All patients were treated by surgery and chemotherapy with or without radiotherapy. Four patients are still alive, and 21 patients died of mediastinal germ cell tumor and its sequelae. Two patients were found to have testicular scars and were dropped from the study. Nongerm cell malignant transformation of a teratoma occurred in five of the remaining 17 patients (29%), resulting in three adenocarcinomas and two sarcomas. Another patient developed leukemia. Metastatic disease most commonly involved the lungs, mediastinal lymph nodes, liver, bone, retroperitoneum, and heart. Respiratory failure was the cause of death in 12 patients. Of the possible mechanisms of germ cell transformation into malignant nongerm cell tumors discussed, this study suggests that chemotherapy alone is unlikely to induce stem cell differentiation. The presence of mature, differentiated teratoma within the primary lesion may be indicative of a poorer prognosis.