Nonseminomatous malignant germ cell tumors can derive from embryonic, extraembryonic (Yolk sac, Choriocarcinoma), or a combination of tissues (mixed germ cell). These tumors typically present as large heterogeneous soft-tissue mass that invades surrounding structures. They oftentimes have central hemorrhage or necrosis. The margins are well circumscribed but irregular with contrast enhancement of the tumor periphery. Invasion of mediastinal structures is extremely common (see SVC syndrome below). Often they are accompanied by pleural or pericardial effusions.

The peak occurrence is age 20-40 predominantly in males (M:F = 9:1). When these tumors occur in children they are equally distributed among males/females. They are associated with Klinefelter syndrome (47 XXY chromosomal abnormality) in 20% of patients. In Klinefelter syndrome, they are typically found in young boys with precocious puberty.

Presenting symptoms include chest pain, dyspnea, cough, weight loss, and fever. In 90%+ of patients there are symptoms of superior vena cava syndrome. Laboratory analysis typically demonstrates elevated serum levels of LDH (60%), hCG (30%), and alpha-fetoprotein (80%).

Treatment is based on cisplatin-based chemotherapy and tumor resection when possible with a long-term survival approaching 50%.