Are Ovarian Cancer and Endometriosis Linked?

Women with ovarian cancer and endometriosis have long asked: Could my endometriosis have caused my ovarian cancer? So far, some studies say yes, some say maybe, and some say no. What is the evidence linking ovarian cancer and endometriosis?

How does cancer develop?

Healthy cells in the body grow and divide at a regular rate. Cells that try to multiply must pass "checkpoints" that monitor for mutations. Cancer cells are basically cells that got past the checkpoints. These cells tend to have serious mutations and grow too quickly, forming tumors.

The basics of endometriosis

The tissue that lines the uterus is called the endometrium. This lining thickens each month during the menstrual cycle. It is then shed during a woman’s period each month. Endometriosis is a chronic condition in which tissue from inside the uterus grows outside the uterus.¹

While endometriosis is not a type of cancer, it does share some of the same features of ovarian cancer. Both conditions are known for:²

• Invading surrounding tissue
• Uncontrolled cell growth
• Forming new blood vessels
• Fewer cells dying off when they are supposed to

Ovarian cancer and endometriosis also share many of the same symptoms, including:^1,2

• Pelvic pain
• Lower back pain
• Painful sex
• Changes in or pain with urinary or bowel habits
• Bleeding between periods or after menopause
• Fatigue

Overlapping symptoms may complicate being diagnosed with ovarian cancer in its early stages when treatment is more likely to be successful.

The link between ovarian cancer and endometriosis

About 1 out of 10 U.S. women have endometriosis. It is even more common in women with chronic pelvic pain or those having trouble getting pregnant. One study found between 4 percent and 29 percent of women with ovarian cancer also have endometriosis. A long-term study of nurses found endometriosis greatly increased the risk of developing ovarian cancer (81 percent to 114 percent).^1-3

Some studies find a strong link between ovarian cancer and endometriosis. But doctors do not fully understand how endometriosis and ovarian cancer may be connected. Some theories include:^2,3

• Endometriosis symptoms may mask or be confused with ovarian cancer symptoms.
• Endometriosis may create a friendly environment for cancer cells by increasing inflammation and changing estrogen levels.
• Genetics may contribute to both conditions.

It is rare, but some women develop atypical endometriosis lesions. These are endometrial cells that become cancerous. However, only 1 out of 100 women with endometriosis develop atypical lesions. So, this is thought to be a rare connection between the 2 conditions.^2-4

Despite this, having both ovarian cancer and endometriosis is rare. The average woman has about a 99 percent chance of never developing ovarian cancer. Women with endometriosis have about a 98.5 percent chance of never developing that cancer. The overall risk of developing ovarian cancer is less than 2 percent even with endometriosis.⁴

Are you living with both ovarian cancer and endometriosis? Connect with others by starting a conversation in Forums.

If you would like to learn more about endometriosis, visit AdvancedOvarianCancer.net’s sister site Endometriosis.net.