Does Endometriosis Cause Cancer?
Endometriosis — a condition where tissue similar to the endometrium grows outside the uterus — affects approximately 10% of women of reproductive age. The relationship between endometriosis and cancer is nuanced: endometriosis is not itself a cancer, but it is associated with an increased risk of certain ovarian cancer subtypes.
The Evidence
Large epidemiological studies have established the following associations:
- Clear-cell ovarian cancer — approximately 3-fold increased risk in women with endometriosis
- Endometrioid ovarian cancer — approximately 2-fold increased risk
- Overall ovarian cancer risk — modestly elevated (relative risk approximately 1.3–1.5)
To put this in perspective: the lifetime risk of ovarian cancer in the general population is approximately 1.3%. A 2–3 fold increase brings this to roughly 2.5–4% — still a low absolute risk. The vast majority of women with endometriosis will never develop ovarian cancer.
Endometriosis-Associated Ovarian Cancer (EAOC)
The biological mechanism is not fully understood, but the prevailing theory is that chronic inflammation and oxidative stress within endometriotic cysts (endometriomas) create a micro-environment that promotes cellular transformation. The presence of an endometrioma — particularly one that is large, long-standing, or has changed in character — warrants specialist assessment.
What Should Women With Endometriosis Do?
- Do not panic — the absolute risk increase is small
- Monitor endometriomas — any change in size, new solid components, or new symptoms should prompt ultrasound reassessment
- Report new symptoms — persistent bloating, pelvic pain that changes character, or new bowel/bladder symptoms after menopause
- Consider specialist review — if you have long-standing endometriosis and are approaching or past menopause, a consultation with a gynaecological oncologist can provide personalised risk assessment
Dr. Nishtha Tripathi Patel manages complex endometriosis and endometriosis-associated ovarian masses in Ahmedabad. Contact: +91 76988 00333.