By Zaira Salvador BSc, MSc (embryologist).
Last Update: 12/22/2017

An ovarian teratoma is an embryonal tumor that contains various cell types. Teratomas typically appear in the ovaries, although it is possible for them to be localized in males and children, particularly in the testes or other body parts.

A teratoma includes several tissues or parts of organs that originate from the three germ layers of the embryo: endoderm, mesoderm, and ectoderm. For this reason, teratomas can contain several tissue types, including hair, teeth, bones, cartilages, etc. This gives teratomas a monster-like appearance.


The term teratoma comes from Greek and is formed by the words teras and onkoma, which literally mean “monster” and “swelling”, respectively. This term is due to the presence of different cell types within the tumor, given that it comes from the embryo’s pluripotent stem cells.

Pluripotent stem cells are defined as a type of cells out of which a complete organism cannot develop, but they can develop into different kinds of cells and tissues corresponding to the embryonic germ layers—endoderm, ectoderm, and mesoderm.

The fact that teratomas look like little “monsters” makes people feel afraid or even terrified when they see pictures of this kind of tumors.

Normally, teratomas are benign tumors, also called mature cystic ovarian teratomas or just mature teratomas. However, at times, teratomas become malignant or cancerous, in which case they are referred to as immature teratomas.

Ovarian or cystic teratomas are the most frequent type of benign tumor detected among women aged 45 or younger.

Also, malignant or immature teratomas are more likely to develop in males than in females, and their typical location is the thorax. In this case, they are known as mediastinal teratomas.


As explained above, there exist two different types of teratomas:

Mature or benign teratomas

Broadly speaking, they tend to appear in women of childbearing age, and they are also known as dermoid cysts. They represent 10-20% of the cases of ovarian neoplasm.

This type of teratomas grow slowly, and their average size ranges between 5 to 15 cm, although there have been cases of 45-cm ovarian dermoid cysts.

Mature teratomas are the type of ovarian tumors that leads to a higher number of complications during pregnancy.

Ovarian teratomas are normally unilateral and tend to appear on the right ovary, although in 15% of the cases they are bilateral and appear on both ovaries. It is also possible to find multiple cysts in a single ovary.

More uncommon locations where mature teratomas can be detected in adults include the skull, mediastinum, retroperitoneal space (retroperitoneum), mesentery, and sacrococcygeal region.

Immature or malignant teratomas

Immature or malignant teratomas are uncommon, but potentially cancerous. In general, they appear among young girls and teenagers younger than 18 years old. They are more frequent in males aged between 20 and 40 years, though.

This type of tumor has a solid aspect with necrosis, composed of immature embryonic tissue, including connective tissue—the one that will develop into the cartilages and bones—, the respiratory tract, and the brain. Even if it is a tiny teratoma, we should consider it as a cancerous one as long as it includes immature tissues.

The term necrosis refers to cellular degeneration in a tissue or organ due to the death of its cells.

We can distinguish between different degrees of severity depending on how expanded the tumor is. If the teratoma has not spread beyond the ovary, its treatment involves the removal of the ovary.

The prognosis depends on the size of the teratoma, its location, the degree of expansion, and the patient’s age.

Causes & Symptoms

The main cause of teratomas is due to an abnormal development of embryonic tissue at some point.

The following is a list with the most common symptoms based on different types of tumor:

  • Mature cystic ovarian teratoma: It is considered asymptomatic. However, it can cause pain on the pelvis, painful intercourse (dyspareunia), infertility, and metrorrhagia (abnormal vaginal bleeding).
  • Testicular teratoma: It is asymptomatic as long as it is benign. Pain on the testis can indicate malignancy.
  • Sacrococcygeal teratoma (SCT): If it is located on the perineum, it can cause discomfort when urinating or defecating.
  • Mediastinal mature teratoma: It can compress certain organs and even compromise your overall health due to its proximity to the heart and the lungs.

There exist other types of teratomas, each one with different symptoms associated. They are, however, infrequent and only represent a small percentage of the population.


Palpating this type of tumors abdominally is considerably complicated. This is the reason why they are normally discovered by accident in routine visits or during surgical interventions such as Caesarian sections. This also explains the size of teratomas, as in the vast majority of cases, an early diagnosis is not possible.

Their presence on the ovary can be confirmed by abdominal or pelvic ultrasound, where a more whitish tissue is seen inside the ovary. The aspect of teratomas through ultrasound scan depends on their size, the site where they are placed, and the level of calcification (accumulation of calcium salts), as well as on the origin of the tissues contained within.

At times, it can be seen through magnetic resonance imaging (MRI) of the pelvis. Moreover, a blood work is required to confirm the presence of the beta-hCG hormone.

To determine whether it is malignant or not, a histological analysis (analysis of the tissues it is composed of) is needed.


Teratomas are treated by means of surgery is all cases. In the case of malignant teratomas, surgery should be accompanied by chemotherapy.

As for mature teratomas, laparoscopy is the least invasive type of surgery to proceed with their removal. On the other hand, immature teratomas can be removed by a surgical procedure called laparotomy, which involves a large incision through the abdominal wall.

Given that most patients are women of childbearing age, it is material in this type of procedures not to cause lasting damages like pelvic adhesions, which could lead to female infertility.

In the most challenging cases, removing both ovaries (oophorectomy) may be necessary, although at times the surgeon considers necessary to remove only part of the ovary to maintain the ovarian function of the woman.

Finally, if it is required to remove both ovaries, the patient will continue to have her uterus intact, in which case she can have children in the future using donor eggs.

If you need to undergo IVF to become a mother, we recommend that you use "The Calculator". In 3 simple steps, it will show you a list of clinics that fit your preferences and meet our strict quality criteria. Moreover, you will receive a report via email with useful tips to visit a fertility clinic for the first time.

Also, the report will inform you about the promotions or special prices that the clinics selected offer so you can benefit from them as well.


The following are the potential complications and side effects associated with teratomas:

  • Torsion, especially in cases of 10-cm or longer teratomas, which can cause you to bleed.
  • Spontaneous rupture, causing chronic peritonitis, infection, adhesions, and compression of the juxtaposed organs.
  • In the case of malignant teratomas, their spread across the body can complicate their removal and worsen the prognosis.

In any case, we recommend that you follow your doctor’s instructions strictly to prevent that symptoms become worse or lead to more severe complications.

FAQs from users

Can teratomas contain eyes?

By Zaira Salvador BSc, MSc (embryologist).

Although teratomas rarely contain more complex organs, there have been cases of teratomas containing parts of eyes (including eyeballs), brain, liver, lungs, or thyroid gland. However, to date, no teratoma containing complete organs has been found.

Can teratomas contain a fetus?

By Zaira Salvador BSc, MSc (embryologist).

This is developmental abnormality known as fetus in fetu in which a mass of tissue that resembles a fetus forms inside the body.

This type of teratoma is also called fetiform teratoma and is characterized by its appearance and the fact that the tissues are well formed. They often appear on the ovary in the form of benign or mature teratomas. They are very uncommon, though.

Suggested for you

Throughout this post, we have talked about the ways in which teratomas can be removed, being one of them laparoscopic surgery. If you want to obtain more information about this type of surgery, visit the following post: Endoscopic Surgery: Hysteroscopy & Laparoscopy.

Egg donation is the fertility option of choice when a woman has to have both ovaries removed. If you want to learn more, click here: Having a Baby through Egg Donation – Early Pregnancy Signs.

Some women make the decision of freezing their oocytes (egg vitrification) when teratomas are malignant and therefore require chemotherapy. Do you want to learn more about fertility preservation techniques? Then, do not miss this guide: Fertility Preservation – Cost & Options for Retaining Your Fertility.

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Authors and contributors

 Zaira Salvador
BSc, MSc
Bachelor's Degree in Biotechnology from the Polytechnic University of Valencia (UPV). Embryologist specializing in Assisted Procreation, with a Master's Degree in Biotechnology of Human Assisted Reproduction from the University of Valencia (UV) and the Valencian Infertility Institute (IVI). More information
License: 3185-CV
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  1. Featured
    scarlett m.

    Hi Sandra, i’ve got a teratoma on my right ovary (5 cm in diameter). My doctor diagnosed it after a simple, routine analysis… it’s not painful at all and i’ve got no symptoms. The strange fact here is that i often have pain on my left ovary, where in principle i’ve got nothing… what’s happening to me?

    • Sandra FernándezBA, MA

      Dear scarlett m.,

      An ovarian teratoma is often asymptomatic. It can, however, lead you to have a general abdominal pain, but it’s uncommon that it causes pain at a particular area of one ovary. My advice is that you describe this situation to your doctor to get more information and have it checked. It’s possible that the pain on the left ovary is due to other reasons, such as ovulation.

      I hope this helps,


  2. Featured

    Hello doc, I’ve had 2 teratomas removed in my life. The second time I had the left ovary removed and currently I’m going through IVF/ICSI treatment with a new teratoma discovered of 6 cm on the right ovary. I’m 28 and today it’s my 4th day after embryo transfer, with an AA quality embryo transferred… What’s your opinion? What do you think are my chances of getting pregnant? Do teratomas affect implantation?
    Thank you very much for your advice!

    • Sandra FernándezBA, MA

      Dear P,

      The presence of a teratoma on one ovary does not affect the chances for embryo implantation. The most important thing in your case is that yours is a AA embryo, which increases your chances of getting pregnant to a large extent.

      I hope this helps,

      Best wishes