Key Points

• Mature teratomas are the most common mediastinal germ cell tumor. Mature teratomas are benign with surgery representing curative therapy.
• Seminomatous germ cell tumors arising in the mediastinum are malignant however have high cure rates with cisplatin-based chemotherapy alone and surgery rarely indicated.
• Nonseminomatous germ cell tumors of mediastinal origin are malignant. Although histologically similar to their more commonly occurring testicular counterparts, primary mediastinal nonseminomatous germ cell tumors have a distinctly worse prognosis and therefore have been categorized as “poor risk” along with other subsets of testicular nonseminomatous germ cell tumors. Cisplatin-based chemotherapy followed by surgical extirpation of residual disease when feasible results in 40% to 50% overall long-term survival.