Evaluating Cancer Risk in Endometriosis

Understanding the Connection Between Endometriosis and Cancer Risk

Endometriosis is not cancerous, but it can exhibit cancer-like behavior by invading tissues and organs or spreading through the lymphatic and blood systems. Research suggests potential molecular links between endometriosis and specific cancers, grounded in genetics and epigenetics (the study of how environmental factors influence gene activity). Overall, the risk of developing certain cancers appears to be slightly increased in women with endometriosis. Additional studies indicate that adenomyosis, a closely related condition, may also be associated with a heightened risk. The reasons remain unclear, though molecular connections are being uncovered, and the degree of risk varies by cancer type.

Endometriosis and Cancer Risk Transformation

Cells from endometriosis can directly transform or degenerate into cancer. The types identified are clear cell, endometrioid, and, more rarely, stromal sarcoma. The exact percentage is unknown due to under-reporting of both endometriosis and these transformation events, but estimates suggest it is only a fraction of 1%. While this fraction is small, the large number of people affected by endometriosis means that tens of thousands may still be at risk.

Endometriosis and Ovarian Cancer Risk

Endometriosis has been linked to an increased risk of developing certain types of ovarian cancer. Studies show that those with endometriosis are more likely to develop clear cell and endometrioid ovarian cancers than those without the condition, with the risk estimated at 1.5 to 3 times higher. The risk is highest when the ovaries are significantly involved, such as with endometriomas.

The mechanisms behind this association are not fully understood, but chronic inflammation and scarring associated with endometriosis may promote cancerous mutations or epigenetic events in cells. Although the risk is increased, most people with endometriosis will not develop ovarian cancer. Still, as with direct malignant transformation, even a small percentage translates to thousands to tens of thousands of affected individuals when considering the overall number of people with endometriosis.

Endometriosis and Thyroid Cancer

Multiple studies consistently report a smaller but statistically significant 1.4-fold higher risk of thyroid cancer in people with endometriosis. The cause is unknown, though some researchers propose a shared autoimmune foundation connecting endometriosis, thyroid disease, and cancer.

Endometriosis and Breast Cancer

Evidence suggests a very small association between endometriosis and breast cancer, with an approximately 4% increased risk. Some studies indicate a somewhat higher risk. However, this association is not as well established as the relationship with ovarian cancer, and further research is needed for confirmation.

Endometriosis and Cervical Cancer

Unlike ovarian and breast cancer, there is no clear link between endometriosis and cervical cancer. A handful of studies even suggest a reduced risk in people with endometriosis, though the reason for this is unknown.

Endometriosis and Other Cancer Risks

While an association with uterine endometrial cancer might be expected, evidence is mixed. A recent meta-analysis reported no increased risk, whereas other studies have found a significantly increased risk in those with endometriosis and adenomyosis. Findings are also conflicting for colorectal cancer; skin cancers, including melanoma; leukemia; lymphoma; urinary cancers; and gastric or liver cancer. Notably, several studies reported no increased colon cancer risk, but one study suggested the risk might be as high as thirteen-fold.

At-a-Glance Summary of Reported Cancer Risks

Managing Your Endometriosis and Cancer Risk

If you have endometriosis, staying informed about potential cancer risks and taking proactive steps can be helpful. Consider regular cancer screening appropriate for your age and personal risk factors, maintain a healthy lifestyle, and discuss any concerns with your doctor. A genetically founded increased risk may be present in some individuals, so if cancer and/or endometriosis runs in your family, consulting an expert may be best. If you are older and have endometriosis, it may also be advisable to seek expert consultation. Awareness and proactive care are valuable, and it is equally important to remember that although risk may be increased, most people with endometriosis will not develop cancer.