Germ cells are cells that populate the gonads and develop into sperm in males and ova in females. They are called germ cells, which is short for “germinate,” a term that means “to grow or develop.”

Sometimes, germ cells may grow out of control and form a tumor. These tumors can arise in ovaries, testes, or occasionally in other locations such as the sacral area (at the bottom of the spine) or mediastinum (the area between the lungs).  

Germ cell tumors are most common among teens aged 15 to 19. It’s one of the more common cancers diagnosed among adolescents in this age range, accounting for about 14% of all teen cancers. Germ cell tumors are also diagnosed among younger children and adults, but it happens less frequently.  

The good news is that adolescents and children who are diagnosed with germ cell tumors usually recover, because there are effective treatments for the condition.  

“Germ cell tumors are one of the most curable types of cancers with 5-year survival rates exceeding 90 percent,” says Yale Medicine pediatric hematologist-oncologist Farzana Pashankar, MD. “They are treated with a combination of chemotherapy and surgery and should be managed by a multidisciplinary team.”

Germ cell tumors are benign (noncancerous) or malignant (cancerous) growths that arise from specialized cells called germ cells, which develop in a baby before birth (a fetus). Germ cells form within the yolk sac, a structure that helps to nourish a fetus before the placenta forms. The germ cells travel from the yolk sac to the fetal midsection, where the reproductive organs form. In males, germ cells transform into sperm within the testes; in females, they transform into eggs within the ovaries.  

Occasionally, some germ cells may mistakenly travel from the yolk sac to other parts of the body, where they may later develop into germ cell tumors in those locations. They also may transform into germ cell tumors within the testes or ovaries.  

When germ cell tumors are benign, they may grow, but they won’t spread beyond the structure where they’re located. When they’re malignant, they have the potential to spread to other organs in the body.  

Germ cell tumors may arise in different body parts, including:

• Testes
• Ovaries
• Brain
• Abdomen
• Chest
• Tailbone

When germ cell tumors occur in the central nervous system (the brain and spinal cord), they often develop close to the pineal gland and pituitary gland, though they can affect other areas of the brain as well. These tumors most commonly affect people between the ages of 10 and 20. They are more common in males than females.

Germ cell tumors are classified by these names, based on their location and tumor type:

• Teratomas, which form in testes, ovaries, and non-reproductive sites and are usually benign
• Dysgerminomas, which form within the ovaries
• Germinomas, which form in brain
• Seminomas, which form in the testes
• Nonseminomatous germ cell tumors (NSGCTs), which are made up of more mature germ cells than seminomas, include:
  • Yolk sac tumors, which are most common among young children and may form in the testes, ovaries, or non-reproductive sites
  • Choriocarcinomas, which are rare and may form in the testes, ovaries, or non-reproductive sites
  • Embryonal carcinomas which are rare and may form in testes, ovaries, or non-reproductive sites
  • Mixed germ cell tumors, which appear in the ovaries, testes, and non-reproductive sites

Doctors aren’t sure what causes germ cell tumors, but some people who have rare inherited conditions affecting the sex chromosomes (X and Y) or reproductive organs may be at increased risk of the condition.

People with germ cell tumors may experience:

• A noticeable mass or lump in the affected body part, such as a testicle
• Pain in the affected body part
• A testicle that is shaped abnormally or is smaller or larger than it should be
• Lump or swelling of abdomen
• Constipation
• Cough
• Trouble breathing
• Headache
• Vomiting

If a child or teen has a suspected germ cell tumor, the doctor will gather information about their medical history, examine them during an office visit, and send them for tests that can confirm the presence of a tumor.  

The doctor will ask questions about an individual’s personal and family health history, to see if the child or adolescent may have an inherited condition that affects the sex chromosomes or reproductive organs, or whether a male may have an undescended testicle.  

During a physical exam for a male, the doctor will feel for a testicular lump or other mass, to see if it may be suggestive of a germ cell tumor.  

Different blood tests may help doctors confirm a germ cell tumor; the tests look for high levels of the following hormones in the blood:

• Alpha-fetoprotein, a hormone that normally appears in a pregnant woman’s blood, as well as the liver and yolk sac of a growing fetus; it’s considered a tumor marker for testicular germ cell tumors.
• Beta human chorionic gonadotropin (hCG), which is sometimes called the “pregnancy hormone,” because it’s found in a pregnant woman’s blood; when a person isn’t pregnant, high levels in the blood may signify a germ cell tumor.

Additionally, doctors may use imaging tests to look for a tumor within the body:  

• Ultrasound
• CT scan
• MRI

When doctors identify a mass they believe may be a germ cell tumor, they will perform a biopsy of the tissue sample. If tissue analysis shows that a germ cell tumor is present, doctors will check to see if the tumor is benign or malignant. Knowing whether or not the tumor is cancerous helps doctors determine treatment.

Children and teens with germ cell tumors typically undergo surgery to remove the tumor. If a biopsy shows that the tumor is benign, removal of the tumor should be the only treatment.  

When the germ cell tumor is malignant, however, the surgeon removes the tumor, as well as a healthy margin of surrounding tissue, with hopes of eliminating all of the cancer cells in the area. Surgery alone may be an effective treatment for some malignant germ cell tumors, depending on individual circumstances. When it isn’t, doctors offer chemotherapy to help eradicate any cancer cells that may be lingering in the body. Sometimes after completion of chemotherapy, further surgery may be needed to remove all remaining sites of disease.

The good news is that most children and teens with malignant germ cell tumors can be treated successfully.

“Germ cell tumors are best treated at a large volume center by a multidisciplinary team,” says Dr. Pashankar. “At Smilow Cancer Hospital in New Haven, we have a dedicated team of oncologists, pathologists, pediatric surgeons, gynecological oncologists, and urologists with expertise in treating germ cell tumors. Our physicians are at the leading edge of research in germ cell tumors and in designing clinical trials for patients with these tumors."

"Treating the individual and family in a patient and family centered approach is very important to us," Dr. Pashankar adds. "As germ cell tumors occur in adolescence and young adults with unique psychosocial needs, we have a dedicated Adolescence and Young Adult program, to help meet the needs of this population and provide holistic care.”