Ovarian teratomas are a type of tumor or mass that develop on the ovaries. The majority are noncancerous and require surgery to remove them.

Teratomas are a type of tumor or mass of cells that develop from one or more layers of germ cells, which are the cells that help form the male and female reproductive systems. The majority of teratomas that occur on the ovaries are benign, with only a few being cancerous.

This article reviews ovarian teratomas, their types, symptoms, causes, and more.

A diagram of the ovaries, where an ovarian teratoma may be present.Share on Pinterest
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Ovarian teratomas are a type of germ cell tumor that contains distinct tissue from three germ cell layers, including the ectoderm, mesoderm, and endoderm. This means that mature teratoma cells may contain:

  • hair
  • muscle
  • teeth
  • bone
  • thyroid tissue
  • fat

There are several different types of ovarian teratomas. Mature cystic teratomas, also known as dermoid cysts, are the most common type of ovarian tumor.

Most mature cystic teratomas are benign, meaning they are not cancerous, but in about 1–2% of cases, they can become cancerous.

Learn more about teratomas here.

Experts classify ovarian teratomas into three broad categories:

  • Mature cystic teratomas: These account for around 20% of all germ cell tumors on the ovaries.
  • Immature teratomas: These contain several different types of cells, many of which may look abnormal under a microscope. They are cancers and can spread to other areas of the body.
  • Monodermal teratomas: These include:
    • struma ovarii, which contains thyroid tissue
    • carcinoid tumors, which contain tissue that helps send messages throughout the body
    • neural tumors, which grow on nerve tissue

In about 6–65% of cases, mature cystic teratomas do not cause symptoms. If symptoms occur, they may include:

In severe cases, mature cystic teratomas may cause:

If the mature teratoma causes an ovarian torsion, a person may experience acute symptoms that can include sudden onset of:

Learn more about ovarian torsion here.

The exact cause of ovarian teratoma is unclear. Experts have presented several theories over the years, which include:

  • They form spontaneously from an unfertilized ovum, or egg, after its first meiotic division. This is a type of division where the parent cell reduces its chromosomes by half to produce four gametes.
  • They form due to an abnormality during the early stages of a fertilized egg’s development.

Researchers continue to look into the exact underlying cause of these growths.

Though the exact cause is unknown, experts have identified several potential risk factors for mature cystic teratomas. They include:

A person may not know they have a mature cystic teratoma until a routine examination where a doctor may discover the mass. Others may discover it due to ovarian torsion, which causes sudden, acute symptoms.

Once a doctor detects it, they will likely order imaging tests. The preferred test is the use of a transvaginal ultrasound. They can typically identify the teratoma based on how it appears on an ultrasound.

Learn more about transvaginal ultrasound here.

Mature cystic teratomas are noncancerous, which means doctors do not stage them. However, about 1–2% of all cases can turn malignant.

Cancerous teratomas follow similar staging to other cancers. A person’s doctor may refer to the cancer as stage 1, 2, 3, or 4.

The stages help doctors explain the overall outlook for the person as well as helping to guide treatment.

Learn more about the stages of cancer here.

For noncancerous mature cystic teratomas, doctors can successfully treat most cases while preserving the ovary. However, even with successful treatment, recurrence can happen within 2–10 years.

Options for management of noncancerous teratomas of the ovaries include:

  • Surveillance: This is suitable for people who are pregnant or who wish to become pregnant and who have a smaller cyst size that is slow-growing.
  • Surgical procedures: Doctors may recommend laparoscopic procedures for younger people with smaller cysts. For people who have gone through menopause with multiple cysts, doctors may recommend an oophorectomy, which is the complete removal of the ovaries.

If the mature cystic teratoma has turned cancerous, a doctor may recommend additional treatment methods that may include:

In cases of immature teratomas, a doctor will likely treat the cancer based on the stage. Complete removal of the ovary and surrounding tissue may be enough for early-stage cancers. A doctor may recommend chemotherapy for more advanced-stage cancers or if the doctor thinks there may still be cancer present.

Mature cystic teratomas that are not cancerous have a high success rate following treatment. In most cases, a doctor can easily remove the teratoma with laparoscopic surgery. Still, a person may have a recurrence of the teratoma within 2–10 years.

In rare cases, a mature cystic teratoma can turn into cancer, and survival rates are relatively low. According to a 2020 study, researchers described the survival rate of this type of ovarian cancer as:

  • 2-year survival rate: 53%
  • 5-year survival rate: 48.4%

They also noted that advanced stages of cancer predict a poorer outcome for the person. In other words, the more advanced the cancer is, the lower the survival rate.

The numbers are much more favorable for people with immature teratomas. According to a 2016 study that reviewed data from over 10 years, the 5-year survival rate for this form of cancerous teratoma was:

  • Stage 1: 98.3%
  • Stage 2: 93.2%
  • Stage 3: 82.7%
  • Stage 4: 72.0%

A person may not realize they have an ovarian teratoma since they will likely not experience symptoms. It is more common for a doctor to discover teratoma during a routine examination.

The Centers for Disease Control and Prevention (CDC) recommend that all women between 18–65 and younger teens who are sexually active get a pelvic exam and Pap smear once a year. A doctor may discover a teratoma during an examination.

A person should also consult a doctor if they experience sudden abdominal pain, nausea, vomiting, or other abdominal symptoms.

Below are answers to some common questions about ovarian teratomas.

Do ovarian teratomas affect fertility?

Ovarian teratomas could affect fertility if they are large enough to block the egg. Also, if they are cancerous and require the removal of one or both ovaries, it can severely impact a person’s fertility.

A person can talk with a doctor about any plans to become pregnant to determine their best options.

How fast do ovarian teratomas grow?

Benign teratomas have a slow growth rate of about 1.8 millimeters per year. A person should consult a doctor about their teratoma’s actual growth rate.

Can teratoma affect pregnancy?

Benign growths during pregnancy may not be an issue if they are small or growing slowly. However, they can cause ovarian torsion, which will require treatment.

Ovarian teratomas are growths made up of germ cells.

In most cases, mature teratomas are noncancerous and rarely become cancerous. Immature teratomas are generally cancerous, but a person has a good chance of survival with treatment.

Typical treatment for teratomas is surgical removal, with a good outlook for most people.