Extragonadal Germ-Cell Tumors

What Is It?

Germ-cell tumors develop from primitive cells that normally mature into ova (eggs) in the ovaries of women and sperm in the testicles of men. Ninety percent of all germ-cell tumors develop within the ovaries and testes; this makes them gonadal. The remaining 10 percent develop outside of the gonads; this makes them extragonadal. Extragonadal germ-cell tumors typically form in the chest, lower back and head.

Many researchers believe that extragonadal germ-cell tumors are related to developmental problems that occur before birth. In the growing embryo, germ cells typically move from a site near the middle of the body to their permanent home in the ovaries or testes. Sometimes, however, there is a problem, and the germ cells never reach their final destination. Instead, the misplaced germ cells settle in the mid-chest area between the lungs, in the lower back just above the buttocks or in the head near the pea-sized pineal gland located in the middle of the brain. When misplaced germ cells grow in these sites, they sometimes develop into tumors, which can be noncancerous (benign) or cancerous (malignant).

Extragonadal germ-cell tumors account for 2 percent to 3 percent of all childhood cancers. In young children, these tumors tend to occur in the lower back. The majority of these tumors are not cancerous. In adults, extragonadal germ-cell tumors tend to occur in the mid-chest area. About 40 percent of these tumors are cancerous. Cancerous extragonadal germ-cell tumors are rare. Only one new case is diagnosed each year for every 2 million to 3 million people in the United States. Cancerous extragonadal germ-cell tumors occur equally in young boys and girls, but in adults, they are nine times more common in men than in women.

There are several types of cancerous extragonadal germ-cell tumors. They are classified as seminomas or nonseminomas. Nonseminomas can be further classified as embryonal carcinomas, malignant teratomas, endodermal sinus tumors, choriocarcinomas or mixed germ-cell tumors. The specific type of germ-cell tumor influences both treatment and prognosis.

Symptoms

Symptoms depend on the location of the tumor:

• Mid-chest area (mediastinum) — Cancerous germ-cell tumors can cause chest pain, breathing problems, cough and fever. They most commonly are diagnosed in men aged 20 to 30.
• Lower-back area (presacral area) — A cancerous germ-cell tumor usually appears as a mass in the lower abdomen or buttocks of an infant or young child. Because of its size and location, the mass may cause difficulty in walking, urinating or having a bowel movement. Noncancerous and cancerous germ-cell tumors are much more common in children than in adults. Tumors in children younger than 6 months old are noncancerous in 98 percent of cases. Tumors in children older than 6 months are cancerous in about 65 percent of cases.