Extraskeletal osteosarcoma of the mediastinum after treatment of a mediastinal germ-cell tumor.

Three years after four cycles of bleomycin, etoposide, and cisplatin (BEP) chemotherapy for a nonseminomatous germ-cell tumor of the mediastinum followed by complete resection of residual teratoma in a 21-year-old man, a mediastinal recurrence was diagnosed as an extraskeletal osteosarcoma. After unsuccessful chemotherapy and removal of the tumor, the patient died of cerebral metastases. Histologic transformation of the teratomatous components of nonseminomatous germ-cell tumors is an uncommon phenomenon showing a particular aspect of germ-cell tumor biology. We review the literature and discuss the pathogenesis concerning this subject.