Thoracic Endometriosis: The Disease We Keep Missing

Why delayed diagnosis, poor recognition, and inadequate standards of care continue to fail patients.

Thoracic endometriosis remains one of the most underrecognized and misunderstood manifestations of the disease. While pelvic endometriosis is finally receiving wider clinical attention, disease involving the diaphragm, pleura, and thoracic cavity still lives in the margins of women’s health.

The result is predictable: delayed diagnosis, confusion among clinicians, fragmented care, and patients who suffer for years before anyone even considers the possibility.

For many patients, the symptoms are highly characteristic. These are not vague complaints. They describe:

• Cyclical shoulder pain (often radiating to the right shoulder)

• Catamenial chest pain (chest pain that aligns with the menstrual cycle)

• Shortness of breath

• Coughing up blood (hemoptysis)

• Recurrent pneumothorax (lung collapse) or hemothorax (blood in the chest cavity)

• A distinct, cyclical decline in athletic performance and stamina

These are often highly functional women who know their bodies well and can identify specific times in the month when they cannot perform normally. Yet even with these distinct patterns, many are dismissed, misdirected, or simply never evaluated for thoracic endometriosis at all.

That failure is not accidental. It reflects a broader structural problem in endometriosis care.

A Disease Hidden by Underfunding and Underdiagnosis

Endometriosis as a whole remains profoundly underfunded relative to its prevalence and burden. Thoracic endometriosis sits even further at the neglected end of that spectrum.

While literature output is growing, it remains a niche field. The body of literature is still dominated by case reports and expert opinions rather than large prospective studies. That matters. When a disease is underfunded, it is under-taught. When it is under-taught, clinicians do not look for it. And when clinicians do not look for it, patients remain undiagnosed.

We already know that a standard endometriosis diagnosis is commonly delayed by 7 to 10 years. Thoracic disease often adds another layer of delay beyond that. Some women will go their entire lives with cyclical shoulder pain or recurrent lung events without ever being told that endometriosis might be the root cause.

Not Benign in Its Consequences

One of the most dangerous myths in endometriosis care is that delayed recognition is acceptable because the disease is somehow “benign.” Thoracic endometriosis proves otherwise.

This is not merely a quality-of-life issue, though its impact there is immense. It can also be a serious and sometimes life-threatening condition. Recurrent pneumothoraces, diaphragmatic defects, and progressive thoracic involvement are not theoretical concerns. Patients may suffer repeated emergency room presentations for years without anyone connecting the pattern. That is a medical systems failure.

Myths That Distort Diagnosis

Thoracic endometriosis is obscured by persistent clinical myths that reduce suspicion and delay referral. Among them:

• That thoracic endometriosis is extremely rare.

• That patients of African heritage are unlikely to have it.

• That menopause eliminates the possibility of disease.

• That chest symptoms in endometriosis patients are too “nonspecific” to pursue.

• That the treatment is essentially the same regardless of whether thoracic disease is formally diagnosed.

How Does Thoracic Endometriosis Happen?

The exact pathogenesis is still not fully understood. The classic explanation is the retrograde menstruation model, where tissue travels upward through the peritoneal cavity to the diaphragm. But on its own, that theory is incomplete.

Other mechanisms likely contribute:

• Coelomic Metaplasia: The pleura and peritoneum share mesothelial origins. Under certain inflammatory pressures, these tissues may transform into endometriotic lesions.

• Lymphatic or Hematogenous Spread: Dissemination through the bloodstream or lymphatic channels may explain distant and atypical thoracic presentations.

• Neuroinflammatory Dysregulation: Thoracic endometriosis appears to behave as a disease shaped by immune dysfunction, fibrosis, and neurobiologic signaling, resembling invasive pathologies more than “benign ectopic tissue.”

The Problem with Current Surgical Thinking

A major obstacle in thoracic care is the assumption that diagnosis does not matter because the surgical treatment is “the same anyway.” That is incorrect.

The quality of surgery, the completeness of treatment, and the structure of the multidisciplinary team matter enormously. There is a dangerous tendency to treat thoracic endometriosis with limited or superficial interventions, particularly when a gynecologic surgeon is uncomfortable with thoracic anatomy.

This is not an area for improvised surgery. Patients with suspected thoracic endometriosis should not encounter thoracic expertise only after an intraoperative surprise. They deserve preoperative counseling, appropriate informed consent, and a planned multidisciplinary strategy involving surgeons who actually understand the disease.

Why Multidisciplinary Care is the Real Standard

Complex endometriosis care cannot rely on ad hoc collaboration. A text message sent to another surgeon from the operating room is not a multidisciplinary program.

When thoracic endometriosis is suspected, cases must be reviewed within an integrated team that includes both gynecologic and thoracic expertise, complete with shared imaging review and surgical planning. Without a true common operative language, misunderstandings between specialties become inevitable.

Imaging Helps—But It Is Not Enough

MRI is currently the most useful modality, especially when the protocol is thoughtfully designed. But even a well-performed MRI has limitations. Thoracic lesions are often subtle, thin, superficial, or fibrotic, falling below the resolution threshold of standard imaging.

In practice, a negative MRI does not exclude disease. CT scans are even less reliable, often missing superficial diaphragmatic disease or pleural abnormalities entirely. This is why thoracic endometriosis remains a clinical diagnosis supported by imaging, not defined by imaging alone.

What the Disease Actually Looks Like

Thoracic endometriosis is not uniform. It can present as:

• Subtle white fibrotic streaks or ribbons

• Blue, brown, or purple lesions

• Superficial pleural implants

• Diaphragmatic fenestrations or “windows”

• Scarred areas of repeated inflammatory injury

• Deeper infiltrative defects involving the full thickness of the diaphragm

Color matters. White lesions often reflect scarring and repeated inflammatory activity. Blue or chocolate-colored lesions may suggest a different stage or phenotype. Because the pleura is built for mechanical stress, it responds to inflammation with rapid, vivid fibrotic reactions, making thoracic lesions look more scarred and nodular than pelvic disease.

The Future: Better Science, Better Teams, Better Standards

Thoracic endometriosis deserves more than curiosity and occasional case reports. It needs:

• More funding to build a confident evidence base.

• Better clinical suspicion so patients are evaluated earlier.

• Standardized multidisciplinary pathways integrating thoracic and gynecologic expertise from the start.

• Better imaging and pathology frameworks tailored specifically to pleural biology.

• A shared classification system to improve global communication and research.

The ESSI Perspective

At ESSI, we believe thoracic endometriosis should be approached with the same seriousness as deep infiltrating pelvic disease: thoughtfully, systematically, and within a multidisciplinary framework. It is not enough to “find a hole in the diaphragm” and call in another surgeon. Patients deserve care from teams that understand both the thoracic and gynecologic dimensions of the disease.

Dr. Francesco Di Chiara, thoracic surgeon, Professor at Oxford University, and ESSI affiliate, has been an important voice in advancing this conversation. His work highlights what many patients already know from lived experience: thoracic endometriosis is real, it is frequently missed, and it can no longer be treated as a fringe curiosity.

The disease is not rare because a few specialists see it. It appears rare because medicine has not looked carefully enough.