Endometriosis and ovarian cancer can share symptoms, affect the same organs, and occasionally appear in the same medical conversation. That combination is enough to make almost anyone’s anxiety sprint a marathon before breakfast.
Here is the reassuring starting point: endometriosis is not cancer, and most people with endometriosis will never develop ovarian cancer. Research does, however, show an association between endometriosis and a higher risk of certain ovarian cancer subtypes. Understanding that connection requires looking at relative risk, absolute risk, disease subtype, age, genetics, symptoms, and the limitations of ovarian cancer screening.
What Is Endometriosis?
Endometriosis is a chronic inflammatory condition in which tissue similar to the lining of the uterus grows outside the uterus. It commonly appears on the ovaries, fallopian tubes, pelvic lining, and tissues surrounding the uterus. It can also affect the bowel, bladder, diaphragm, and, in uncommon cases, areas outside the pelvis.
These growths are benign, meaning they are not cancerous. Benign, however, does not mean harmless. Endometriosis can contribute to inflammation, scarring, adhesions, severe menstrual pain, pain during sex, painful bowel movements, urinary symptoms, heavy bleeding, infertility, fatigue, and digestive complaints. When endometriosis affects an ovary, it may form a blood-filled cyst called an ovarian endometrioma, sometimes nicknamed a “chocolate cyst” because of its dark contents. Medical terminology occasionally has the naming instincts of a dessert menu, but the condition itself is no treat.
Symptoms vary dramatically. One person may have extensive disease with limited pain, while another may have small lesions and symptoms that regularly disrupt work, sleep, relationships, exercise, and daily routines. Symptom severity alone does not reliably reveal how much endometriosis is present.
What Is Ovarian Cancer?
“Ovarian cancer” is an umbrella term covering several diseases. Some cancers begin in ovarian cells, while others grouped under the ovarian cancer category may begin in the fallopian tube or nearby peritoneal tissue. Epithelial cancers are the most common group, but epithelial ovarian cancer itself contains biologically distinct subtypes.
Major epithelial ovarian cancer subtypes include:
- High-grade serous carcinoma
- Low-grade serous carcinoma
- Endometrioid carcinoma
- Clear-cell carcinoma
- Mucinous carcinoma
These cancers do not share identical causes, growth patterns, treatments, or relationships with endometriosis. The endometriosis connection is most consistently observed with clear-cell ovarian carcinoma and endometrioid ovarian carcinoma, not with every ovarian cancer subtype.
Does Endometriosis Cause Ovarian Cancer?
Current evidence supports an association, but saying that endometriosis directly “causes” ovarian cancer oversimplifies the science. Most endometriosis lesions remain benign throughout a person’s life. Only a small fraction appear to undergo the cellular changes associated with malignant transformation.
Large observational studies and systematic reviews have found that people diagnosed with endometriosis have a higher relative risk of ovarian cancer than those without the condition. A major meta-analysis reported that the association was strongest for clear-cell and endometrioid tumors. A large 2024 study also found that risk varied substantially by endometriosis type, with ovarian endometriomas and deep infiltrating endometriosis associated with the greatest increases.
Relative risk is not the same as absolute risk
This distinction is essential. Relative risk compares one group with another. Absolute risk describes the actual chance of developing a disease.
Imagine that one condition occurs in one person out of 100 in a particular population. If another group has twice the relative risk, its risk would be approximately two out of 100not 50 out of 100. The relative increase sounds dramatic, while the absolute increase remains modest.
In the 2024 research summarized by the National Institutes of Health, women with endometriosis had more than four times the ovarian cancer risk of women without endometriosis. Yet the estimated absolute difference was approximately 10 additional ovarian cancer cases per 10,000 women during the study period. That is a meaningful research finding, but it also shows why headlines without context can generate more heat than light.
Which Forms of Endometriosis Have the Strongest Connection?
Ovarian endometriomas
An endometrioma develops when endometriosis grows within an ovary and forms a cyst. Because the lesion exists directly in ovarian tissue, researchers have paid particular attention to its possible relationship with clear-cell and endometrioid ovarian cancers.
Having an endometrioma does not mean cancer is present or inevitable. Most ovarian endometriomas are benign. Nevertheless, a cyst that develops suspicious features, changes rapidly, becomes increasingly complex, or appears after menopause may require closer evaluation.
Deep infiltrating endometriosis
Deep infiltrating endometriosis grows beneath the surface of pelvic tissues and may involve structures such as the bowel, bladder, ureters, vagina, or ligaments supporting the uterus. Recent observational research has associated this severe endometriosis subtype with a higher ovarian cancer risk than superficial disease, although more work is needed to determine how those findings should affect long-term monitoring.
Atypical endometriosis
Pathologists occasionally identify atypical cellular changes in surgically removed endometriosis tissue. Atypical endometriosis is considered a possible intermediate step between ordinary endometriosis and some endometriosis-associated ovarian cancers. This finding is microscopic; it cannot be diagnosed from symptoms alone or by inspecting a medical illustration on the internet at 2 a.m.
Why Might the Conditions Be Connected?
No single mechanism fully explains the relationship. Researchers are investigating several overlapping biological processes.
Chronic inflammation
Endometriosis creates a local inflammatory environment. Persistent inflammation may expose nearby cells to chemical signals and oxidative stress that can damage DNA over time. Inflammation does not automatically create cancer, but it may help build conditions in which abnormal cells are more likely to survive and multiply.
Repeated bleeding and oxidative stress
Endometriomas contain old blood and iron-rich breakdown products. Excess iron can contribute to oxidative stress, which may injure cells and genetic material. Researchers suspect that prolonged exposure to this environment may play a role in the development of some clear-cell and endometrioid tumors.
Hormonal influences
Endometriosis is influenced by estrogen. Hormonal signaling may help lesions persist, stimulate cellular growth, and interact with inflammatory pathways. The relationship is complicated, however, and estrogen exposure alone does not explain who develops ovarian cancer.
Accumulated genetic alterations
Studies of endometriosis-associated ovarian tumors have identified molecular changes affecting pathways involved in cell growth, DNA repair, and tumor suppression. Some mutations can also be detected in nearby benign or atypical endometriosis tissue, suggesting that certain cancers may develop through a gradual, multistep process rather than appearing overnight. These discoveries are scientifically important but are not currently used as routine at-home or office screening tests.
Endometriosis Symptoms Versus Ovarian Cancer Symptoms
Symptom overlap is one reason the topic is confusing. Both conditions can cause pelvic pain, abdominal discomfort, bloating, fatigue, and bowel or bladder changes. A single symptom rarely identifies the cause. Its timing, persistence, intensity, and departure from your normal pattern matter more.
| Symptom or pattern | Often seen with endometriosis | May warrant evaluation for an ovarian mass |
|---|---|---|
| Pelvic pain | Frequently cyclical and worse around menstruation | New, persistent, progressive, or unrelated to the menstrual cycle |
| Bloating | May fluctuate around periods or with bowel symptoms | Persistent bloating or increasing abdominal size |
| Eating changes | Nausea may occur during painful periods | New early fullness or reduced appetite |
| Urinary symptoms | May worsen during menstruation, especially with bladder involvement | New urgency or frequency that continues |
| Bowel changes | Constipation, diarrhea, or painful bowel movements around periods | Persistent changes without a clear explanation |
| Bleeding | Heavy periods or bleeding between periods | Any bleeding after menopause or an unexplained new pattern |
Ovarian cancer symptoms can be subtle and nonspecific. Common warning signs include persistent bloating, abdominal or pelvic pain, feeling full unusually quickly, urinary changes, bowel changes, fatigue, and unexplained weight changes. These symptoms are far more often caused by noncancerous conditions, but they should not be ignored when they are new, frequent, persistent, or worsening.
Should People With Endometriosis Receive Routine Ovarian Cancer Screening?
For most asymptomatic people without a known hereditary cancer syndrome, routine ovarian cancer screening is not recommended. The U.S. Preventive Services Task Force recommends against screening average-risk, asymptomatic women because available methods have not been shown to reduce ovarian cancer deaths and can produce false-positive results, unnecessary anxiety, and avoidable surgery.
Why ultrasound is not a universal screening test
Transvaginal ultrasound is useful for evaluating symptoms and examining a known ovarian cyst or mass. It can describe size, structure, blood flow, solid areas, and other features. It cannot reliably determine whether every mass is benign or malignant, and using it repeatedly in asymptomatic, average-risk people has not been proven to save lives.
Why CA-125 is not a stand-alone cancer test
CA-125 is a blood marker that may be elevated in ovarian cancer. It can also rise for benign reasons, including menstruation, pelvic inflammation, fibroids, pregnancy, and endometriosis. Some ovarian cancers do not produce elevated CA-125 at an early stage. For those reasons, the result must be interpreted alongside age, symptoms, imaging, menopausal status, medical history, and other findingsnot treated like a red or green traffic light.
When Might Additional Monitoring Be Appropriate?
Care should be individualized. A clinician may recommend imaging, follow-up, specialist consultation, or surgery when a person has:
- A new or enlarging ovarian mass
- An endometrioma with changing or complex imaging features
- Persistent symptoms that differ from the person’s usual endometriosis pattern
- A mass discovered after menopause
- A strong family history of ovarian, breast, pancreatic, colorectal, or endometrial cancer
- A known or suspected BRCA1, BRCA2, Lynch syndrome, or other hereditary cancer-related variant
- Unexplained weight loss, increasing abdominal size, early satiety, or persistent urinary changes
Genetic risk can matter more than endometriosis alone. People with relevant personal or family histories may benefit from formal cancer-risk assessment and genetic counseling.
Can Endometriosis Treatment Reduce Ovarian Cancer Risk?
Treatment decisions should primarily address pain, fertility goals, quality of life, organ involvement, cyst characteristics, age, and personal preferences. Endometriosis should not automatically be treated with major surgery solely because of cancer fear.
Hormonal therapiesincluding certain birth control pills, progestin-based treatments, and other medicationscan reduce endometriosis activity and symptoms for many patients. Oral contraceptive use has also been associated with a lower ovarian cancer risk in the general population, although individual benefits and risks should be discussed with a clinician.
Surgery may be appropriate for severe symptoms, infertility treatment, organ involvement, concerning masses, or large endometriomas. Removing both ovaries sharply reduces ovarian cancer risk but causes immediate surgical menopause and can affect bone, cardiovascular, sexual, cognitive, and overall health. It is not a casual “better safe than sorry” procedure.
For people already undergoing pelvic surgery for another medical reason, opportunistic removal of the fallopian tubes while preserving healthy ovaries may be discussed. This strategy is based on evidence that many high-grade serous cancers originate in the fallopian tubes. It does not eliminate every ovarian or peritoneal cancer risk, and it is not specifically required for every person with endometriosis.
Questions to Ask Your Healthcare Professional
- What type and location of endometriosis do I have?
- Does my ovarian cyst look like a typical endometrioma?
- Has the cyst changed in size or appearance?
- Which symptoms should prompt an earlier appointment?
- Does my family history suggest a need for genetic counseling?
- Would additional imaging change my treatment plan?
- What are the fertility consequences of surgery?
- Should a gynecologic oncologist review my imaging before surgery?
- What are the benefits and harms of removing a cyst, tube, or ovary?
Bringing a written list is not being difficult. It is being efficient. Medical appointments can make perfectly articulate people forget every question except, “Where did I park?”
Experiences Related to Endometriosis and Ovarian Cancer Concerns
The following is a fictional composite designed to reflect experiences commonly described by patients. It is not a real patient record and should not be interpreted as medical guidance for a specific person.
At 34, “Maya” had already spent years organizing her life around pelvic pain. She kept pain relievers in her purse, desk, car, and travel bag. She declined plans during the first days of her period and learned which grocery-store aisle offered the shortest route to the restroom. After several appointments in which her symptoms were attributed to stress, ordinary cramps, or digestive trouble, an ultrasound identified an ovarian cyst that appeared consistent with an endometrioma.
The diagnosis brought two conflicting emotions: relief that the pain finally had a name and fear after she searched for information online. Within minutes, she encountered phrases such as “ovarian cancer risk,” “malignant transformation,” and “ninefold increase.” The numbers felt enormous, but the context was nowhere in sight. She began treating every episode of bloating as a possible emergency.
At her follow-up appointment, her gynecologist explained the difference between relative and absolute risk. Endometriosis increased the likelihood of certain ovarian cancer subtypes, but the overall probability remained low. Her cyst had the smooth, uniform appearance expected of an endometrioma, and it had not changed significantly on repeat imaging. The doctor did not dismiss her fear. Instead, they created a plan: document symptoms, repeat imaging at a clinically appropriate interval, and return sooner if she developed persistent early fullness, steadily increasing abdominal size, unexplained weight loss, or pain that felt distinctly different from her established pattern.
Maya also learned that monitoring did not mean ordering every test every month. A CA-125 result could be elevated because of endometriosis itself. Repeated ultrasounds could discover harmless findings that led to more tests without improving outcomes. Her plan needed to be purposeful, not driven by panic.
She started using a symptom diarynot because an app could diagnose cancer, but because patterns were easier to discuss when written down. She tracked cycle dates, pelvic pain, bowel symptoms, appetite, bloating, medication use, and missed activities. Over several months, she noticed that most symptoms rose and fell with menstruation. That information helped her clinician evaluate change rather than relying on a vague memory of whether the previous Tuesday had been “kind of bad.”
Fertility added another layer. Surgery might reduce pain and remove the cyst, but ovarian surgery could also affect ovarian reserve. Maya met with an endometriosis specialist and a fertility specialist before choosing treatment. The conversations were not simple, but they were more useful than treating cancer fear as the only factor. She eventually chose conservative surgery because of increasing pain and cyst growth, not because she believed every endometrioma was a ticking time bomb.
The pathology report confirmed benign endometriosis. Her anxiety did not vanish instantly, but it became more manageable. She understood that future symptoms still deserved attention and that no test could provide a lifetime guarantee. She also understood that living under constant suspicion of cancer carried its own cost.
Experiences like this reveal why communication matters. Patients need more than “don’t worry,” because worry rarely obeys commands. They need clear explanations of absolute risk, an individualized follow-up plan, specific warning signs, and space to discuss fertility, menopause, sexuality, work, and mental health. The goal is neither alarm nor complacency. It is informed attention.
Conclusion
Endometriosis is a benign inflammatory disease, not a form of cancer. Research nevertheless indicates that it is associated with an increased risk of ovarian cancer, particularly clear-cell and endometrioid carcinomas. The strongest associations appear among people with ovarian endometriomas or deep infiltrating endometriosis.
Even with that increased relative risk, ovarian cancer remains uncommon among people with endometriosis. Most will never develop it. Routine screening with CA-125 or ultrasound is not recommended for every asymptomatic person, because these approaches can produce false alarms without clearly reducing mortality.
The most useful strategy is individualized care: understand your endometriosis subtype, know your family history, monitor meaningful changes, seek evaluation for persistent symptoms, and discuss concerning ovarian masses with an experienced specialist. Good care should replace vague fear with a practical planbecause your ovaries may be complicated, but your medical information does not have to be.
