What Is a Teratoma?

Table of Contents
View All
Table of Contents

Teratomas are a rare type of germ cell tumor, meaning they start in reproductive cells that can produce eggs or sperm. They may be malignant (cancerous) or benign (noncancerous).

A teratoma may be diagnosed before birth through a routine sonogram (imaging using sound waves) taken during pregnancy. Teratomas are also seen in newborns, children, and young adults.

The most common sites for teratomas are the ovaries (organs that produce eggs), the testes (organs that produce sperm), and the tailbone in babies. Teratomas may also form in the neck and chest.

A person receives a sonogram from healthcare professional (Types of Teratomas)

Verywell / Jessica Olah

Teratomas can contain many types of tissue because they are produced by cells that can form all three germ layers of an embryo (ectoderm, mesoderm, and endoderm). These tumors contain fully formed tissues and organs such as skin, teeth, muscle, bone, and hair from two or three germ layers.

Often, teratomas form from germ cell tumors that contain other cell types.

Types of Teratomas

Teratomas are classified as mature or immature. Both types require medical treatment, such as surgery.

Mature Teratomas

Mature teratomas start out as benign but can become malignant if not treated. They are often diagnosed before birth or in newborns. They can be found in the testes or ovaries of adolescents or young adults.

These tumors can grow very large but do not spread throughout the body, the way cancer cells do.

Mature teratomas may form and grow inside the body. This can cause compression of the internal organs. They can also grow on the outside of the body. These are more likely to be identified on an ultrasound. Some mature teratomas form both inside and outside the body.

Mature teratomas can be:

  • Solid: Comprised of firm tissue containing blood vessels
  • Cystic: One or more fluid-filled cysts in a self-contained sac with a thin outer rim
  • Mixed: Have both cystic and solid parts

Immature Teratomas

Around 1% of all teratomas are immature. This type of teratoma is malignant. Immature teratomas are most likely to be found in the ovaries of females or testes of males. Immature teratomas are typically diagnosed in adolescents and young adults.

Tumor Location

Teratomas are also identified by their location in the body:

  • Cervical (neck)
  • Mediastinal (chest)
  • Sacrococcygeal (tailbone)
  • Ovarian
  • Testicular

Teratoma Symptoms

Teratoma symptoms vary based upon the size and location of the tumor. In many instances, the tumor may be visible. Tumors that aren’t visible might be felt under the skin. For example, testicular teratomas can cause lumps or swelling that can be felt or seen in the testicle.

In addition to lumps, there can be other physical symptoms or abnormal lab results.

High Levels of Alpha-Fetoprotein (AFP)

If you’re pregnant and your fetus has a teratoma, you may have elevated levels of this protein in your blood. Alpha-fetoprotein is routinely checked early in the second trimester of pregnancy to screen for various conditions. AFP is produced in the liver, fetal yolk sac, and gastrointestinal tract of developing fetuses.

High levels of AFP can signal fetal conditions including teratomas. Too-high AFP can also indicate germ cell cancer in the testes or ovaries of adolescents or adults.

High Levels of Beta-Human Chorionic Gonadotropin (B-HCG)

B-HCG is produced by the placenta. It is routinely checked during pregnancy. Elevated blood levels can indicate germ cell tumors and other types of cancers. B-HCG rarely is elevated due to a teratoma but can be elevated if there is a germ cell tumor that includes a portion of teratoma.

Trouble Breathing

Cervical teratomas and mediastinal teratomas in newborns and babies can lead to breathing difficulties.

Cervical teratomas are large congenital (present at birth) masses that form in the neck. They can make it impossible for a newborn to breathe. Cervical teratomas are often diagnosed prenatally and surgically removed during a caesarean delivery (C-section).  

Mediastinal teratomas grow between the lungs. This type of teratoma can also make it hard for a newborn to breathe and may also affect the heart.

Pain and Weakness

Sacrococcygeal (tailbone) teratomas can cause weakness in the lower extremities, painful or difficult urination, constipation, and stomach pain. This type of teratoma is often diagnosed prenatally.

Teratomas in the ovaries of adolescents or young adults can cause extreme pelvic and abdominal pain. This results from ovarian torsion (twisting of the ovary).


During fetal development, cells start to differentiate and migrate to different areas of the body. Teratomas are caused by a problem with the cell differentiation process. That’s why a teratoma contains tissues that belong in other parts of the body. Why this problem arises is not completely known or understood.


Diagnostic tests that can help uncover teratomas include:  

  • Biopsy (surgical removing a sample of the tumor for testing in a lab)
  • X-ray
  • Blood tests
  • Magnetic resonance imaging (MRI)
  • Computed tomography (CT) scan
  • Ultrasound (sonogram)

Sonograms are a routine part of prenatal care. When a fetus has a teratoma growing on the outside of its body, it may be diagnosed before birth during an ultrasound of the pregnant parent.

Teratomas may be diagnosed after birth if they cause symptoms such as lumps or swelling. If a teratoma is suspected in a newborn, imaging tests such as X-rays and CT scans will be used to make a diagnosis.

Lumps indicating ovarian teratomas are sometimes discovered during gynecological exams. Testicular lumps may be found during routine physicals. You may also notice a lump during bath time or a diaper change.

Teratomas may remain undiagnosed until they cause symptoms, such as pain.


Teratomas must always be surgically removed. Mature (benign) teratomas can be disfiguring, and very large in size. Even though they’re not malignant, they can cause devastating outcomes in newborns when not treated. Mature teratomas can also become cancerous over time. 

If a teratoma is diagnosed during pregnancy, you’ll have sonograms often to assess the growth and size of the teratoma and its impact on your baby’s health. In some instances, fetal surgery may be done to drain fluid from the teratoma, but usually the teratoma will be surgically removed immediately after birth.

After surgical removal, your child will continue to be monitored for tumor regrowth annually for several years.

When teratomas occur in the ovary, surgical removal is required. Mature ovarian teratomas are treated by removing part or all of the ovary.

Treatment for immature (cancerous) ovarian teratomas often includes chemotherapy (medications that kill fast-growing cells, such as cancer cells) as well as surgery. The stage of your tumor (whether it can be completely removed or has spread) will determine the type of treatment you need.

Mature and immature testicular teratomas are typically treated with an orchiectomy (surgical removal of the testicle). Cancerous tumors may also require chemotherapy after surgical treatment.


Yours or your child’s prognosis is affected by several factors, including whether the teratoma is malignant or benign.

The surgical procedures done to remove mature teratomas on babies can be challenging and complicated. When surgery is successful, the baby’s prognosis is typically good, and they’ll go on to live a normal life. Ongoing monitoring is required however to make sure that the tumor doesn’t return.

If you have an immature ovarian teratoma, your prognosis will be affected by the stage of your cancer. The five-year survival rate for a stage 1 tumor (least advanced) is 98.3%. The five-year survival rate for a stage 4 tumor (most advanced, with the cancer having spread to other parts of the body) is 72%.

Prepubertal (detected before puberty) testicular teratomas are typically benign and have a highly favorable prognosis. Testicular teratomas in adults metastasize (spread to other sites) up to 60% of the time. This type of teratoma has a less favorable prognosis. 


If you or your partner are pregnant with a baby who has a teratoma, your mind may be reeling. Because this condition is so rare, it can be hard to find a support network that will fit your specific situation. Finding support, however, may be essential for getting through the next several months. Your healthcare professional or a therapist may be good resources.

Mapping out a game plan with your healthcare team to monitor pregnancy and delivery is also essential. In some instances, you may determine that your current medical team is unequipped to handle delivery and pediatric treatment of a teratoma.

If that's the case, trust your gut, and ask your healthcare provider for a referral to a specialist or a children's hospital or other facility that are a better fit. Don't worry about how your current healthcare provider may feel. They likely aren't trained for this type of condition. Knowing that you have the right medical team in place will enable you to cope and relax. It may also ensure a better outcome.

Practicing self-care during this time can help. Think about stress-relieveing strategies like meditation, nature walks, and prenatal yoga. It's also OK to avoid time with pregnant people who aren't going through the same situation if it upsets you to be around them. No matter what, don't take on more than you can handle.

If you or your older child has a teratoma, take a deep breath. Teratomas are treatable and usually come with a favorable prognosis. If you have a malignant teratoma, a cancer support group may be beneficial. CanCare and the American Cancer Society are good places to start.


Teratomas are a rare type of germ cell tumor. Most teratomas are benign. Teratomas that are left untreated can become cancerous over time. Many teratomas are discovered in fetuses during pregnancy via ultrasound of the pregnant parent. Others may not emerge until puberty or later.

Teratomas in adolescents and young adults often affect the reproductive organs. Many of these are benign and respond well to treatment. Malignant teratomas are treated surgically and sometimes with chemotherapy.

A Word From Verywell

Getting a diagnosis for a rare condition is difficult, especially when there is lack of knowledge and support from others. If you or your child is faced with a teratoma, stay informed. Don’t be afraid to ask your doctor questions. Make sure you understand your treatment options and the plan that is in place for you. If necessary, get a second opinion. Seek support from people you trust. Many resources can help you get through this. 

12 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Phi JH. Sacrococcygeal teratoma: A tumor at the center of embryogenesisJ Korean Neurosurg Soc. 2021;64(3):406-413. doi:10.3340/jkns.2021.0015

  2. Alwazzan AB, Popowich S, Dean E, Robinson C, Lotocki R, Altman AD. Pure immature teratoma of the ovary in adults. Int J Gynecol Cancer. 2015;25(9):1616-1622. doi:10.1097/IGC.0000000000000541

  3. Boston Children's Hospital. Teratoma | symptoms & causes.

  4. American College of Obstetricians and Gynecologists. Prenatal genetic screening tests.

  5. MedlinePlus. Alpha-fetoprotein (AFP) test.

  6. Boston Children's Hospital. Cervical teratoma.

  7. Nicklaus Children's Hospital. What is mediastinal teratoma?

  8. Boston Children's Hospital. Teratoma | diagnosis & treatment.

  9. American Cancer Society. Ovarian germ cell tumor treatment | ovarian teratoma treatment.

  10. Farci F, Shamsudeen S. Testicular teratoma. In: StatPearls. StatPearls Publishing; 2021.

  11. Jorge S, Jones NL, Chen L, et al. Characteristics, treatment and outcomes of women with immature ovarian teratoma, 1998–2012. Gynecol Oncol. 2016;142(2):261-266. doi:10.1016/j.ygyno.2016.05.024

  12. Wetherell D. Mature and immature teratoma: a review of pathological characteristics and treatment optionsMed Surg Urol. 2014;03(01). doi:10.4172/2168-9857.1000124

By Corey Whelan
Corey Whelan is a freelance writer specializing in health and wellness conntent.