Association between mediastinal germ cell tumors and hematologic malignancies. Report of two cases and review of the literature.

A hematologic malignancy occurred simultaneously with a malignant mediastinal germ cell tumor in two men. In one instance the blood disorder was acute nonlymphocytic leukemia, and in the other, malignant histiocytosis. We subsequently identified nine additional patients, all male (age range 12-48 years), with a mediastinal germ cell tumor and either acute nonlymphocytic leukemia or malignant histiocytosis. Six of the 11 patients had not received either radiation or chemotherapy before development of the hematologic malignancy. One patient developed malignant histiocytosis and was found to have a malignant mediastinal germ cell tumor after having received steroid therapy for a renal allograft. The four remaining patients developed acute nonlymphocytic leukemia 5-32 months after initiation of irradiation or chemotherapy for a mediastinal germ cell tumor. In four patients with acute leukemia, karyotypic analysis established the clonal nature of the leukemic process. Although the leukemia may be therapy-related in four or possibly five patients, this explanation cannot be applied to the remaining six patients. These six patients, coupled with studies of in vitro growth characteristics of teratocarcinoma cells described previously, suggest that a previously unrecognized association between malignant mediastinal germ cell tumors and hematologic malignancies may exist in humans.