This page was reviewed under our medical and editorial policy by

Maurie Markman, MD, President, Medicine & Science

This page was reviewed on May 2, 2022.

A teratoma is a relatively rare type of tumor. Your cells are constantly multiplying to make new cells. When this process goes awry and new cells are created unnecessarily, or old cells stay alive instead of dying, they can cluster together and form a tumor.

Although the direct causes of teratomas aren’t well understood, the origins go back to before birth, when a baby is developing in its mother’s womb. Early on in development, an embryo’s cells are undifferentiated, meaning that they can become all different types of cells and go on to form the various structures that make up a human body. As development continues, these cells spread throughout the body and mature, becoming differentiated and taking on their own identity to perform specific functions.

One type of cell, called a germ cell, is supposed to go to the ovaries or testicles and turn into egg or sperm cells. Teratomas are made up of germ cells, and they form when these cells start multiplying rapidly.

But a teratoma isn’t just any tumor. As a teratoma forms, the germ cells turn into different types of cells—including hair cells, bone cells and muscle cells—similar to the process of cell differentiation that occurs in an embryo. The resulting teratoma is a collection of tissues, such as skin, hair, muscle, bone and teeth. The name “teratoma” derives from the Greek word “teras” for “monster.”

Teratomas can be malignant (cancerous) or benign (not cancerous). Malignant tumors can spread to other parts of the body and form new tumors. Benign tumors don’t spread, but they can still cause problems as they get bigger. Teratomas are most often benign, although the likelihood of a malignant teratoma depends on factors such as the tumor’s location and the patient’s age. Benign teratomas are called mature, while teratomas that are likely cancerous are called immature. Mature teratomas are more common than immature teratomas.

  • Mature teratomas aren’t likely to become cancer. These tumors contain cells that look very similar to the normal, healthy cells in your body. In most cases, mature teratomas can be treated if the tumor can be completely removed by surgery. However, some mature teratomas can come back after they’re removed.
  • Immature teratomas are more likely to be cancerous and spread to other parts of the body. The cells contained in an immature teratoma resemble the immature cells that make up an embryo.

Because they start in the sperm or egg cells, most teratomas grow in the ovaries or the testicles. Teratomas that occur in the ovaries or testicles are called gonadal teratomas. Teratomas that grow outside of the gonads (ovaries or testicles) are called extragonadal teratomas.

Gonadal teratomas include:

  • Teratoma in the ovaries: Teratomas are the most common benign tumors that grow in the ovaries. Almost all are benign. Benign ovarian teratomas are often called dermoid cysts. They most commonly affect women during their reproductive years (after puberty and before menopause).
  • Teratoma in the testicles: These tumors usually affect children younger than age 4 or adolescents/young adults. In young children, testicular teratomas are typically benign. In adolescents and young adults, they’re more likely to be cancerous.

Extragonadal teratomas include:

  • Teratoma in the tailbone area: These tumors are most common in infants. They tend to develop before birth. They are rarely cancerous, but they always require surgical removal. Teratomas in the tailbone area are the most common tumor that affects infants.
  • Teratoma in the neck area: These tumors most commonly occur in children and are usually benign. Teratomas of the neck very rarely affect adults, and they tend to be cancerous when they do.
  • Teratoma in the mediastinum (area separating the lungs): These tumors are rarely malignant, but when they are, they typically affect young men.
  • Teratoma in the brain/spinal cord: These tumors most often occur in adolescents between the ages of 10 and 19, and they’re more common in males than females.

Teratoma symptoms and diagnosis

The symptoms that may indicate a teratoma can be entirely different depending on the tumor’s location and size. They’re also often indistinguishable from the symptoms that come with other types of tumors. As a result, they can sometimes be discovered by accident. For example, your doctor may find a teratoma in the ovaries while performing a cesarean section.

Below are some of the potential symptoms of a teratoma, according to its location:

  • Teratoma in the ovaries
    • Recurring abdominal pain
    • Bloating
    • Irregular menstrual cycle
  • Teratoma in the testicles
    • Testicular pain
    • Mass or lump in the testicles
  • Teratoma in the neck (cervical teratoma)
    • Wheezing
    • Noisy breathing
    • Difficulty breathing
    • Shortness of breath
    • Difficulty swallowing
  • Teratoma of the mediastinum
    • Chest pain
    • Cough
    • Tiredness
    • Lack of endurance
    • Shortness of breath

These are just a few examples of the areas where teratomas can develop and the symptoms that may come with them. Many teratomas, especially when they’re small, cause no symptoms at all.

The process of diagnosing a teratoma also depends on where the tumor is growing. The following diagnostic tests may help establish a diagnosis:

A biopsy is the most important diagnostic test, as a teratoma diagnosis cannot be confirmed until a tumor sample is microscopically analyzed. In a laboratory, a pathologist, who has expertise in diagnosing diseases, will examine the cells contained in the tumor sample. If the cells clearly indicate a teratoma, a pathologist will need to determine whether the teratoma is mature or immature.

Treatment for teratomas

The potential treatment options for a teratoma vary widely, and treatment decisions are primarily influenced by whether the tumor is malignant or benign. Of course, other factors also play a role, such as your preferences and the tumor’s location and size.

For most teratomas, the primary treatment is surgery to remove the tumor. Chemotherapy isn’t considered to be “very effective” against teratomas, according to the American Society of Clinical Oncology. Chemotherapy may be used if a tumor is a mixture of teratoma and other types of germ cell tumors.

Below are some examples of potential treatment options for teratomas, depending on your age and the tumor’s location:

Childhood teratomas in the ovaries, testicles, tailbone, abdomen or neck: Children with mature or immature teratomas in these areas will be treated with surgery to take out the tumor. After surgery, the child will be monitored through regular checkups to see whether the tumor returns. Late-stage immature teratomas in children may sometimes be treated with chemotherapy after surgery, but doctors are unsure whether the addition of chemotherapy is beneficial in these cases.

Childhood teratomas in the brain or spinal cord: Children with mature or immature teratomas in the brain or spinal cord will be treated with surgery to remove the tumor while limiting damage to essential structures as much as possible. After surgery, if the surgeon couldn’t remove the entire tumor, radiation therapy or chemotherapy may be used.

Adult ovarian teratoma: For a teratoma in the ovaries, surgeons remove the part of the ovary that contains the tumor or the entire ovary. This is the only treatment needed for a mature teratoma in the ovaries. For immature (cancerous) tumors in the ovaries, chemotherapy may be needed before or after surgery to help prevent the tumor from recurring.

Adult testicular teratoma: This type generally requires surgical removal of the testicle that contains a teratoma.

Adult teratoma in the neck: Most patients with benign or malignant teratomas in the neck will undergo surgery to take out the tumor. Benign tumors in the neck can cause breathing problems or other complications if they aren’t removed. Malignant teratomas in the neck may be treated with radiation therapy before surgery.

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