Germ cell cancer can develop in children and adults. Researchers don’t know exactly what causes germ cell cancers to form, but they have identified some risk factors.

Germ cell tumors are abnormal growths that form in the cells that become eggs or sperm. Roughly 20% are cancerous, and the remainders are noncancerous.

Most germ cell cancers form in the testicles or ovaries, but they can develop almost anywhere in your body.

According to the National Cancer Institute, more than 90% of testicular cancers start in germ cells. Ovarian germ cell tumors make up about 2% to 3% of ovarian cancers.

Germ cell cancers can develop in children or adults. They’re estimated to make up 3% of childhood cancers and about 15% of cancers diagnosed during adolescence.

In this article, we take a deeper look at germ cell cancers, including who’s at risk, how they develop, and how they’re treated.

Illustration showing common sites for germ cell tumors in children and adultsShare on Pinterest
Common locations of germ cell tumors in children and adults. Illustration by Antonio Jimenez

Germ cell cancer develops in cells that become eggs or sperm. It usually develops in your ovaries or testes, but it can also develop in other places. According to the National Cancer Institute, it can occur almost everywhere.

Studies from Northern Europe estimate that testicular germ cell tumors occur in 80 to 100 men per million. It’s the most common cancer in men between puberty and age 40.

Ovarian germ cell cancer makes up about 15% to 20% of ovarian cancers overall and about 75% of cancerous ovarian tumors in children. In a 2019 study, researchers estimated the number of cases in North America from 2008 to 2012 as:

AgeOvarian germ cell cancers per million people
0 to 91.4
10 to 197.8
20 to 397.2

Extragonadal germ cell cancer

When germ cell cancer develops outside your ovaries or testicles, it’s known as extragonadal germ cell cancer. In adults, extragonadal germ cell cancer only makes up about 4% of germ cell cancers. It makes up almost half of germ cell cancers in children.

It’s not clear why extragonadal cancers develop, but it’s thought to do with how germ cells develop before birth. When a fetus grows in the womb, cells that produce eggs or sperm usually move to the testes or ovaries. Sometimes, though, they settle in other body parts. The most common places they settle are:

  • at the base of the spine
  • brain
  • chest
  • abdomen

Some of the more common types of germ cell cancers include:

  • Teratomas: Teratomas are tumors that can be cancerous. They most often develop in your tailbone or reproductive organs.
  • Germinomas: Germinomas are referred to as dysgerminomas when they occur in your ovaries and seminomas if they develop in your testicles. Germ cell cancers that develop in the testicles are usually classified as seminomas or nonseminomas.
  • Yolk sac tumor: Yolk sac tumors most often develop in the reproductive organs or tailbone. They’re the most common testicular cancer in children.
  • Choriocarcinoma: Choriocarcinoma is a cancerous tumor that usually forms in the placenta and can affect the fetus and mother. It tends to grow rapidly and is very rare.
  • Embryonal carcinoma: Embryonal carcinoma usually forms in the testicles of adolescent males. About 40% of testicular tumors have features of this cancer, but only 3% to 4% are pure embryonal carcinoma.

Symptoms of germ cell cancer depend on where the cancer develops. The vast majority of germ cell cancers in adults occur in the testicles or ovaries.

Testicular germ cell cancer may cause:

According to the National Cancer Institute, ovarian germ cell tumors often don’t cause early symptoms. When symptoms do appear, they may include:

General symptoms of extragonadal germ cell tumors include:

Researchers don’t know exactly why germ cell cancers form, but they have identified some conditions that seem to increase the odds of developing them:

  • Klinefelter syndrome: Klinefelter syndrome is when a person assigned male at birth has an extra X chromosome.
  • Androgen insensitivity syndrome: This condition develops when a person who’s assigned male at birth is insensitive to male hormones.
  • Turner syndrome: Turner syndrome is when a girl is born missing an X chromosome.
  • Cryptorchidism: Cryptorchidism is when a male child is born with an undescended testicle.

People assigned male at birth are at a higher risk of developing germ cell tumors overall. However, in children, those assigned female at birth develop germ cell tumors about 25% more often.

Testicular germ cell tumors most often occur before the age of 4 or in adolescence to young adulthood. Other risk factors for testicular germ cell tumors include:

Ovarian germ cell tumors most commonly occur in adolescent girls or young women.

Doctors start the diagnostic process by performing a physical exam and considering your medical history.

Imaging can be used to locate a tumor. Your doctor may order:

Blood tests often reveal tumor markers called alpha-fetoprotein and human chorionic gonadotrophin that are suggestive of germ cell cancer.

Doctors can confirm a diagnosis by taking a small tissue sample called a biopsy so that the cells can be analyzed in a lab. Sometimes, the cancer can be diagnosed without a biopsy with the results of imaging and blood tests alone.

The best treatment for germ cell cancer depends on factors such as:

  • how advanced the cancer is
  • where the cancer is located
  • your overall health
  • your age

Extragonadal germ cell treatment

According to the National Cancer Institute, three standard treatments are used for extragonadal tumors:

  • surgery
  • radiation therapy
  • chemotherapy

High-dose chemotherapy with stem cell transplant is being investigated in clinical trials.

Testicular cancer treatment

Five types of standard treatments are used to treat testicular cancer:

Ovarian germ cell cancer treatment

Treatment options for people with ovarian germ cell cancer includes:

  • surgery
  • chemotherapy
  • radiation therapy
  • high-dose chemotherapy with bone marrow transplant

Treatment for germ cell cancers not located in the head

In children, standard treatment for germ cell cancers not in the head include:

  • surgery
  • observation
  • chemotherapy

Clinical trials are examining:

  • targeted therapy
  • radiation therapy
  • high dose chemotherapy with stem cell transplant

Your outlook if you have germ cell cancer depends on the specific type of cancer you have and where it’s located. Many types have high chances of survival.

Someone’s outlook is generally better for germ cell cancer found in their testicles or ovaries than in other places. Reproductive function is usually preserved when only one ovary or testicle is removed.

The 5-year survival rate for ovarian germ cell cancer is about 95% for stage 1 and 83% for stage 2 to 5.

The 10-year cancer-specific survival rate for stage 1 testicular germ cell cancer is about 99.7%. This means that only 3 out of 1,000 people die from factors related to the cancer within 10 years.

The 5-year survival rate for testicular germ cell cancer that has spread to other body parts is around 48% to 64% for people in the highest-risk group.

For children under 15, the 5-year survival rate for ovarian and testicular germ cells is about 90%. It’s about 93% for teens ages 15 to 19.

A small number of children develop long-term side effects from treatment that may develop years later. These side effects include kidney problems, lung problems, and hearing loss.

Germ cell cancer starts in the cells that become sperm or eggs. They can develop in almost any part of your body if these cells spread while you’re still developing in the womb.

Your outlook with germ cell cancer depends on which type of cancer you have. Many types have high survival rates and can be managed with treatments such as chemotherapy, surgery, or radiation therapy.