Epidemiology & Pathology
Extragonadal germ cell tumors are rare, accounting for approximately 3% of all germ cell tumors. Debate continues over whether these lesions originate from “burned-out” testicular primaries or originate de novo. Most retroperitoneal tumors have their origin from a testicular primary, whereas mediastinal germ cell tumors are truly ectopic.

The most common sites of origin in decreasing order are mediastinum, retroperitoneum, sacrococcygeal area, and pineal gland. All germ cell types may be observed. Seminoma composes more than half of the retroperitoneal and mediastinal tumors.

Clinical Findings
Clinical presentation depends on the site and volume of disease. Mediastinal lesions may present with pulmonary complaints. Retroperitoneal lesions may present with abdominal or back pain and a palpable mass. Sacrococcygeal tumors are most commonly seen in neonates and may present with a palpable mass and bowel or urinary obstruction. Pineal tumors may present with headache, visual or auditory complaints, or hypopituitarism.

Metastatic spread is to regional lymph nodes, lung, liver, bone, and brain. Metastatic workup is similar, therefore, to that of testicular germ cell tumors. A careful testicular examination is mandatory along with ultrasonography to exclude an occult testicular primary.

Treatment & Prognosis
Treatment of extragonadal germ cell tumors parallels that of testicular tumors. Low-volume seminoma can be managed with radiotherapy. High-volume seminoma should receive primary chemotherapy. Prognosis parallels that of testicular seminoma. Primary chemotherapy should be employed for nonseminomatous elements with surgical excision of residual masses; however, prognosis remains poor for these patients.