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 follo wed by complete resection of residual teratoma in a 21-year-old man, a medi astinal recurrence was diagnosed as an extraskeletal osteosarcoma. After un successful chemotherapy and removal of the tumor, the patient died of cereb ral metastases. Histologic transformation of the teratomatous components of nonseminomatous germ-cell tumors is an uncommon phenomenon showing a parti cular aspect of germ-cell tumor biology. We review the literature and discu ss the pathogenesis concerning this subject.