Most women associate endometriosis with pelvic pain, painful periods, or bowel and bladder symptoms. But in rare cases, endometrial-like tissue can grow far outside the pelvis — on the diaphragm or even inside the chest cavity. This is known as thoracic endometriosis, and it can cause symptoms that have nothing to do with the abdomen at all: shoulder pain, chest pain, or difficulty breathing, often appearing in a pattern linked to the menstrual cycle.

Because these symptoms mimic musculoskeletal, cardiac, or lung problems, thoracic endometriosis is frequently missed or misdiagnosed for years. If you are in Mumbai or elsewhere in India and have unexplained, cyclical shoulder or chest symptoms alongside a history of endometriosis, understanding this rare presentation could be the key to finally getting an accurate diagnosis.

What Is Thoracic and Diaphragmatic Endometriosis?

Thoracic endometriosis refers to endometrial-like tissue found within the chest cavity, most commonly on or near the diaphragm, but occasionally on the lung surface (pleura) or lung tissue itself. When the tissue is limited to the diaphragm, it is often called diaphragmatic endometriosis.

This tissue behaves the same way it does in the pelvis — it responds to hormonal changes during the menstrual cycle, which is why symptoms often flare in a cyclical pattern, typically appearing just before or during menstruation.

It is considered one of the rarest forms of endometriosis, and it overwhelmingly affects the right side of the diaphragm and chest, for reasons still being studied by researchers.

Common Symptoms of Thoracic Endometriosis

Symptoms vary depending on exactly where the tissue is located, but often include:

• Right shoulder-tip pain that recurs with each menstrual cycle
• Chest pain, often on the right side, worsening around periods
• Shortness of breath during menstruation
• A dry cough that follows a monthly pattern
• Coughing up small amounts of blood during periods (in rare, more advanced cases)
• Sudden lung collapse during menstruation, known as catamenial pneumothorax — a rare but serious complication

Because these symptoms are cyclical, they often appear and disappear on their own, which can delay a woman from seeking evaluation or lead a doctor to dismiss the symptoms as unrelated to gynaecological health.

Why Is It So Often Misdiagnosed?

Thoracic endometriosis is frequently mistaken for other conditions because chest and shoulder symptoms are rarely the first thing that comes to mind when evaluating a gynaecological condition. Common misdiagnoses include:

• Musculoskeletal shoulder strain or referred muscular pain
• Anxiety-related chest tightness or breathlessness
• Asthma or recurrent chest infections
• Cardiac causes of chest pain
• Pleurisy or other lung conditions unrelated to hormones

Women are often sent to pulmonologists, cardiologists, or orthopaedic specialists before a gynaecological connection is even considered — especially if they have not yet been diagnosed with pelvic endometriosis. This is part of the reason endometriosis already takes years to diagnose in India; rare presentations like thoracic disease can add several more years to that delay.

Who Is at Risk?

Thoracic endometriosis most often occurs in women who already have, or previously had, pelvic endometriosis, particularly:

• Women with a history of deep infiltrating endometriosis
• Women with diaphragmatic involvement discovered incidentally during pelvic surgery
• Women aged 30 to 40, though it can occur at other ages
• Women whose cyclical chest or shoulder symptoms have never been connected to their menstrual cycle

However, some women present with chest symptoms as their very first sign of endometriosis, with no prior pelvic diagnosis.

How Is It Diagnosed?

Diagnosing thoracic endometriosis usually involves a combination of:

• Detailed symptom history — noting whether chest or shoulder symptoms follow a monthly, cycle-linked pattern
• Chest X-ray or CT scan — especially if performed during menstruation, when abnormalities are more likely to be visible
• MRI of the diaphragm and chest — can help identify diaphragmatic nodules
• Video-assisted thoracoscopic surgery (VATS) — the most definitive way to visually confirm and treat lesions inside the chest
• Pelvic evaluation — to check for coexisting pelvic or bowel endometriosis, which is common in these cases

Timing imaging around the menstrual cycle significantly improves the chances of catching abnormalities that might otherwise be missed.

Treatment Options for Thoracic Endometriosis

Treatment depends on the severity of symptoms and whether complications like pneumothorax have occurred.

Hormonal Therapy

Suppressing the menstrual cycle with hormonal treatment can reduce or eliminate cyclical flare-ups in mild cases by limiting the hormonal stimulation of the endometrial-like tissue.

Surgical Management

For confirmed diaphragmatic or pleural lesions, surgical excision — often via VATS in coordination with a thoracic surgeon — is usually the most effective long-term option, particularly when there is a risk of recurrent lung collapse.

Combined Gynaecological and Thoracic Approach

Because thoracic endometriosis frequently coexists with pelvic or diaphragmatic disease, a coordinated approach between a gynaecological surgeon experienced in advanced endometriosis and a thoracic surgeon often gives the best outcomes, addressing both the chest findings and any pelvic disease in a single treatment plan.

When Should You See a Specialist?

You should seek evaluation if you notice:

• Shoulder or chest pain that consistently appears around your period
• Breathlessness that seems to follow a monthly pattern
• A history of endometriosis along with new, unexplained chest symptoms
• Sudden chest pain and breathlessness during menstruation (this needs urgent medical attention to rule out pneumothorax)

Because thoracic endometriosis is rare, it requires a specialist who recognises the pattern and knows when to refer for chest imaging or thoracic surgical evaluation alongside gynaecological care.

If you are looking for expert endometriosis care in Mumbai, Dr. Shinjini Pande is an experienced Consultant Obstetrician, Gynaecologist, and Advanced Laparoscopic Surgeon who evaluates both common and rare presentations of endometriosis, including extra-pelvic disease. She works closely with allied specialists to ensure that unusual symptom patterns are correctly diagnosed and treated.

If your chest or shoulder pain seems to follow your menstrual cycle, don’t dismiss it as unrelated. Schedule a consultation to discuss your symptoms and find out whether they could be connected to endometriosis.

Frequently Asked Questions (FAQs)

1. Can endometriosis really affect the lungs or chest?

Yes. In rare cases, endometrial-like tissue can grow on the diaphragm, the lining of the lungs, or lung tissue itself, causing chest and shoulder symptoms tied to the menstrual cycle.

2. Why does thoracic endometriosis mostly affect the right side?

Researchers believe it may be related to the direction of pelvic fluid flow and the anatomy of the right diaphragm, though the exact cause is still being studied.

3. Is catamenial pneumothorax an emergency?

Yes. Sudden chest pain and breathlessness during menstruation, especially if severe, requires immediate medical attention to rule out a collapsed lung.

4. Do I need to have pelvic endometriosis to develop thoracic endometriosis?

Not always. While many women with thoracic endometriosis also have pelvic disease, some are diagnosed with chest symptoms first, with no prior pelvic diagnosis.

5. How is thoracic endometriosis treated?

Treatment may involve hormonal therapy to suppress cyclical flare-ups, or surgical removal of the affected tissue, often performed jointly by a gynaecological surgeon and a thoracic surgeon.