An Overview of Endometrioma

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Endometrioma, also called ovarian endometrioma or endometrioid cyst, is a type of cyst formed when endometrial tissue grows in the ovaries. These cysts are benign and estrogen-dependent. Endometrioma is part of a condition known endometriosis.

Endometriosis is a painful condition where endometrial tissue grows outside the uterus. It affects women in their reproductive years and causes chronic pelvic pain often associated with menstruation. Some women with endometriosis may have fertility problems. Endometriosis affects up to 15% of women of reproductive age, with up to 8% experiencing endometrioma. Endometrioma is often associated with more severe forms of endometriosis.

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Endometrioma may cause symptoms for some women, but not all women experience symptoms. The size of a cyst does not matter in the type of symptoms or severity of symptoms.

In other words, even a woman who has a small cyst can experience symptoms and pain, or a woman with a large cyst might not have symptoms or only have mild symptoms. Ovarian endometrioma rarely exceeds 15 centimeters in width, but some can be up to 20 centimeters in size. The largest-ever endometrioma seen was 26 centimeters.

When endometrioma symptoms do occur, they are similar to the symptoms of endometriosis. These may include:

  • Painful periods
  • Pelvic pain, not related to monthly periods
  • Irregular, and sometimes, heavy periods
  • Pain during sexual intercourse
  • Infertility for some women

If an ovarian endometrioma ruptures, you may experience severe, sudden abdominal and pelvic pain on the side where the cyst is located. This can be a medical emergency.

Medical attention should be sought if severe pain is experienced or if you suspect you have ruptured a cyst.

Signs of a ruptured cyst include:

  • Intense abdominal and/or pelvic pain: Pain will be sharp and sudden or numbing in the lower abdominal area on the side of the ruptured cysts.
  • Bleeding: Ruptured cysts are known for happening during monthly periods, and as a result, they may be missed. If bleeding during your period is significant and you are experiencing severe pain, immediately talk to the doctor who is treating you for endometriosis.
  • Dizziness, nausea, vomiting, and low-grade fever are all common symptoms of a ruptured cyst.


Researchers don’t know for sure what causes endometrioma. One theory is that endometrioma forms due to retrograde menstruation, which may also explain endometriosis.

According to Endometriosis Foundation of America, retrograde menstruation refers to a women’s menstrual blood flow going back into her body during her period. Menstrual debris carries tissue away from the endometrium, the lining of the uterus that sheds monthly.

With retrograde menstruation, the endometrial cells are carried backward through the Fallopian tubes, ovaries and pelvic cavity where they implant and cause endometriosis to develop.

With endometrioma, endometrial cells attach and implant into the ovaries causing cysts to develop. The lining of these cysts behaves in the same way the lining of the uterus does. It grows and sheds monthly in response to female hormones. However, instead of leaving the body, endometrial tissue is trapped in the cysts, causing inflammation and changing the way the ovaries function.


Your doctor may suspect endometrioma if you have endometriosis and are experiencing symptoms or have unexplained fertility. A cyst can also be felt during a pelvic exam.

Ultrasounds are good at identifying the presence of cysts, but they are not helpful in determining the type of cyst you have. To confirm if a cyst is endometrioma, your doctor will want to test fluid and debris from the cyst during a needle biopsy. 

During the biopsy, your doctor will use ultrasound to help guide the needle through the vagina to the endometrioma. The fluid and tissue samples are then examined under a microscope to determine if they contain endometrial cells, which is a key indicator of endometrioma.


How your doctor treats endometrioma depends on several factors. This may include your age, symptoms, whether one or both ovaries are affected, and your plans for having children going forward. 

Small cysts that are not causing symptoms are usually not treated, but your doctor will want to take a watch-and-wait approach. Birth control pills may be recommended to inhibit ovulation, manage pain, and slow down cyst growth.

Slowing down cyst growth will not keep cysts from growing or new ones from developing. Even after surgery, some women may experience new cyst growth.

Surgery to remove cysts—called ovarian cystectomy—is recommended for women who have painful symptoms, large cysts, cysts that might be suspect for cancer, and infertility. This procedure is done using a laparoscope, a thin, long tube with a camera and light to help the doctor to perform the procedure. The laparoscope is inserted through a small incision. 

Doctors do not like to perform ovarian cystectomies, as they could potentially contribute to infertility and negatively affect ovarian function. The pros and cons of this procedure must be weighed, as for some women, the inflammation and toxicity of having endometrioma are more harmful.

There is also the potential for malignancy in tumors greater than 4 centimeters. Surgery is also recommended in cases where a woman is in severe pain.

A Word from Verywell

Endometrioma is common in women who have endometriosis. Your symptoms can usually be managed with medication, and surgery is an option when medication does not help.

Endometrioma and surgical treatments may affect fertility. Talk to your doctor about all your treatment options. Let your doctor know if you are considering having children in the future. All these things help with developing an appropriate treatment plan.

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  2. Yaşar L, Süha Sönmez A, Galip Zebitay A, et al. Huge ovarian endometrioma—a case report. Gynecol Surg. 2010;7:365. doi:10.1007/s10397-009-0482-6

  3. Sampson’s Theory of Retrograde Menstruation. Endometriosis Foundation of America.

  4. Deep Ovarian Endometriosis (Endometriomas). Brigham and Women's Hospital.

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