Germ cells are the cells in a developing fetus that eventually produce sperm in males and eggs in females. These cells normally develop along what's called the "midline" of a fetus (usually where the stomach and other internal organs will lie) before finally settling into place in the reproductive organs.
Abnormal groupings of germ cells that cluster together, becoming tumors, tend to develop in the ovaries or testes. Sometimes, though, because germ cells can settle in other places along their way to the reproductive organs, tumors can form in other areas.
The most common sites for germ cell tumors outside of the reproductive tract are the mediastinum (part of the chest between the breastplate and spine), tailbone, abdomen, and pelvis. Some also might develop in the central nervous system.
Types of Tumors
Like tumors that occur elsewhere in the body, germ cell tumors can be benign (not cancerous) or malignant (cancerous). There are several different types; each is classified according to the specific types of germ cells present and their location in the body.
The most common germ cell tumors include:
- Teratomas. These tumors are usually benign, but can be malignant. In children, teratomas on the tailbone are the most common type of germ cell tumor. Fortunately — because they're often easy for parents and doctors to see and feel — teratomas in this area usually are detected early and respond well to treatment.
- Germinomas. These tumors are malignant. Although they can affect both males and females, they tend to occur most frequently in the ovaries of adolescent girls. Girls may feel abdominal pain or have constipation, and if the tumor has had time to grow, it may be felt as a lump in the abdomen.
- Endodermal sinus (or yolk sac) tumors. Although these tumors can be benign, they're more often malignant and can be quite aggressive. They're most commonly found in the ovaries, testes, or tailbone.
- Embryonal carcinoma. This malignant tumor is usually a mixture of several different types of cells. It occurs most often in a boy's scrotum, but can spread (metastasize) elsewhere in the body.
- Choriocarcinoma. This less common, often malignant tumor arises from the placenta during pregnancy and can affect both the mother and child. It's most common in pregnant teens, but can also affect girls who are not pregnant but still have placental cells from their own mothers present in their bodies.
The cause of most germ cell tumors is not well known. Doctors do know that certain medical conditions can make a child more likely to develop a germ cell tumor. These include birth defects that affect the central nervous system, genitals, urinary tract, and spine; as well as certain genetic conditions that result in missing or extra sex chromosomes. Boys with undescended testicles (testes that remain up inside the pelvis) also appear to be at a slightly increased risk.
Early on, a child with a benign or malignant germ cell tumor might have few symptoms or none at all. As the tumor grows, however, a mass may be felt or seen in the abdomen or elsewhere in the body.
Other symptoms include constipation or trouble holding urine if the mass is in the pelvis, leg weakness if the tumor is pressing on the nerves at the base of the spine, and a testicle that is abnormal in shape or size.
A doctor who suspects that a child has a tumor will perform a thorough physical exam in addition to these tests:
- Imaging studies. These might include a CT scan, MRI, X-ray, ultrasound, and bone scans. Not only are these tests helpful in determining the size and location of the tumor, they also can help determine if cancer has spread to other parts of the body.
- Biopsy. A biopsy is when a piece of tissue is removed from the body for further examination in a lab. This closer look helps doctors make a diagnosis (such as cancer) and choose the right treatment. A biopsy often can be performed laparoscopically (using a small incision and a camera to guide the doctor's movements instead of more invasive surgery).
- Blood tests. Tests such as a complete blood count, liver and kidney function panel, and blood chemistries can give important information about how well the liver and other organs are functioning. An alpha-fetaprotein (AFP) or beta-human chorionic gonadotropin (β-HCG) test measures for elevated levels of these proteins in the body, which can indicate the presence of a tumor. If the doctor suspects the tumor is related to an underlying genetic condition, certain genetic tests also might be done.
Children with benign germ cell tumors will undergo surgery to remove the tumor. Those with malignant tumors will receive treatment after a process called staging.
Staging is a classification system (usually using roman numerals l-lV) that helps doctors determine how far the cancer has progressed. It takes into account things like the size of the tumor (or tumors), how deeply the tumor has penetrated an organ, and whether the tumor has metastasized to nearby or distant organs.
This information, in addition to a child's age and overall heath, helps doctors develop treatment plans that may include the following options, in combination or alone:
- Surgery. Kids with malignant tumors also may have surgery to remove as many of the cancerous cells as possible. Depending on the size and location of the tumor, they might undergo minimally invasive surgery, which requires a shorter hospital stay and recovery period.
- Radiation therapy. This treatment uses high-energy radiation from X-rays, gamma rays, or fast-moving subatomic particles (called particle or proton beam therapy) to target and destroy cancer cells. Besides killing cancer cells, radiation therapy can also harm normal cells, causing physical side effects like fatigue, nausea, and hair loss. During treatment a child's health care team will take extensive measures to carefully monitor radiation doses to protect healthy tissue as much as possible. Most side effects go away once treatment has ended.
- Chemotherapy. In contrast to radiation, which destroys the cancerous cells of a tumor in a specific area of the body, chemotherapy works to treat cancer throughout the body. Several chemotherapy drugs are often combined to attack the cancer cells in different ways. Like radiation, side effects are likely, but most will subside once treatment ends.
The stress of having a child who is being treated for any type of tumor can be overwhelming. And being told that a child has cancer can be a terrifying experience.
To find out about support that may be available to you or your child, talk to your child's doctor or a hospital social worker. Many resources are available to help you get through this difficult time.
Reviewed by: Donna Patton, MD
Date reviewed: September 2009