Mediastinal Germ Cell Tumors

Germ cell tumors are neoplasms that typically occur in the gonads where they originate from multipotential primitive germ cells. Occasionally, these tumors are found to arise in extragonadal sites, usually along midline structures, such as the pineal gland, retroperitoneum, mediastinum, and sacral area. Extragonadal germ cell tumors are thought to develop from germ cells that are misplaced during their migration from the yolk endoderm to the gonads during early embryogenesis and can display the same spectrum of neoplasms native to the testis and ovary. Primary mediastinal germ cell tumors are rare, accounting for approximately 1-3% of all germ cell tumors, 15% of all anterior mediastinal tumors in adults and 24% in children. Germ cell tumors with benign behavior are more common in females and children, while the vast majority of malignant mediastinal germ cell tumors occur in older adolescent and adult male patients. In the mediastinum, these tumors are characteristically located in the anterior compartment, within or close to the thymic gland, although lesions arising in the posterior mediastinum, pericardium, and aortic adventitia have been reported.