Can Endometriosis Cause Cancer? Understanding the Real Risk

Can endometriosis cause cancer? It’s one of the most anxious questions people search after a diagnosis. The honest answer: there’s a small but real elevation in risk for certain ovarian cancers — but the absolute risk remains low, and endometriosis itself is not classified as cancer. This article cuts through the panic and lays out what the research actually shows.

For background see What is Endometriosis? and What Causes Endometriosis?.

The straight answer

Endometriosis is a benign (non-cancerous) condition. It does not transform into cancer in most cases. However, large epidemiological studies have shown a modest increase in the risk of certain types of ovarian cancer for people with endometriosis. The numbers:

• Endometrioid and clear cell ovarian cancers: about 1.3-1.9× increased risk compared to the general population
• The general population’s lifetime risk of ovarian cancer is roughly 1.3%
• For people with endometriosis, that becomes approximately 1.7-2.5% lifetime risk — still low in absolute terms

That means: even with elevated relative risk, the vast majority (over 97%) of people with endometriosis will not develop ovarian cancer.

What we know about the mechanism

The link is most clearly established for two specific subtypes: endometrioid ovarian cancer and clear cell ovarian cancer. Both can develop within endometriomas (the ovarian cysts that form in endometriosis).

Possible mechanisms being studied:

• Chronic inflammation within endometriomas can lead to cellular mutations over time
• Genetic mutations (particularly in ARID1A and PIK3CA genes) found in both endometriomas and the related cancers
• Repeated hormonal stimulation and bleeding inside endometriomas

Important: endometriosis is not linked to elevated risk for the most common ovarian cancer (high-grade serous), which has different origins.

What about other cancers?

Some studies have suggested very modest associations between endometriosis and breast cancer, melanoma, and non-Hodgkin lymphoma. These associations are small and not consistently replicated. They don’t justify alarm, but they may explain why some studies report a slight overall elevated cancer risk.

Conversely: endometriosis appears to be protective against cervical cancer (likely because of more frequent gynecological monitoring).

What you can do

Three concrete things that matter more than the cancer-risk question:

1. Stay engaged with your gynecological care. Regular monitoring of endometriomas (size, growth, changes) is part of standard endometriosis follow-up.
2. Use hormonal suppression where appropriate. Beyond pain management, hormonal therapy reduces the formation of new endometriomas and may lower long-term cancer risk.
3. Take changes seriously. A rapidly growing endometrioma, new mass on the ovary, or persistent abdominal swelling after menopause warrants prompt evaluation — not because cancer is likely, but because catching anything early matters.

Reading the research carefully

Studies on this topic have caveats worth understanding:

• Most data come from registry studies, which can have selection bias (people with severe endometriosis are more likely to be tracked)
• Relative risk numbers (“1.3-1.9× increased”) sound scary but translate to small absolute changes when starting from a low base rate
• Hormonal treatment patterns aren’t always fully controlled for in studies, and hormonal suppression itself may modify risk

The bottom line of most expert reviews: elevated relative risk exists, but the absolute risk stays low enough that no special cancer-screening protocol is currently recommended for people with endometriosis beyond standard gynecological care.

Frequently asked questions

Does endometriosis turn into cancer?

Endometriosis itself doesn’t “turn into” cancer in most cases. But the lining of endometriomas (ovarian endometriotic cysts) can, very rarely, develop cellular changes leading to specific ovarian cancer subtypes. Absolute risk stays low — over 97% of people with endometriosis don’t develop ovarian cancer.

How much does endometriosis increase ovarian cancer risk?

The relative risk for endometrioid and clear cell ovarian cancers is roughly 1.3-1.9 times the general population. That translates to an absolute lifetime risk of approximately 1.7-2.5% (versus 1.3% baseline) — still low.

Should I have more frequent screenings if I have endometriosis?

Standard endometriosis follow-up already includes regular gynecological care and monitoring of endometriomas — that’s the most effective “screening” available. There’s no specific cancer-screening protocol recommended for endometriosis beyond standard care. Talk to your doctor about your individual risk profile.

Does removing endometriomas reduce cancer risk?

Surgically removing endometriomas eliminates the tissue where these specific cancers could potentially develop, so it may reduce risk — but ovarian surgery also reduces ovarian reserve. The decision involves balancing cancer risk reduction against fertility preservation. For most people, monitoring rather than prophylactic removal is recommended.

Does hormonal therapy increase or decrease cancer risk?

Hormonal suppression of endometriosis (combined pill, progestins, etc.) appears to be neutral or slightly protective for endometriosis-associated ovarian cancer. Long-term hormonal contraceptive use is generally associated with reduced ovarian cancer risk in the general population.

Sources

1. Pearce CL et al. Association between endometriosis and risk of histological subtypes of ovarian cancer: a pooled analysis of case-control studies. Lancet Oncol 2012;13:385–394.
2. Kvaskoff M et al. Endometriosis and cancer: a systematic review and meta-analysis. Hum Reprod Update 2021;27:393–420.
3. ESHRE. Endometriosis Guideline. 2022.
4. Wilbur MA, Shih IM, Segars JH, Fader AN. Cancer implications for patients with endometriosis. Semin Reprod Med 2017;35:110–116.