In some people with endometriosis, the endometrium-like patches grow on or around the lungs. This can cause coughing, chest pain, and shortness of breath.

Thoracic endometriosis is rare, and it can be hard to identify. It can take up to 4 years to identify the condition.

Typically, endometriosis patches grow in the lower abdomen and pelvic area. However, when they grow on and around the lungs, they may be life threatening. Complications can cause bleeding or a collapsed lung.

Read more to learn about what thoracic endometriosis is, its symptoms, how it is diagnosed, and how it is treated.

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Endometriosis is a relatively common condition affecting roughly 6–10% of reproductive-age females. It causes tissue similar to the uterine lining to grow outside the uterus.

In most cases, endometriosis patches grow in the abdomen and pelvic areas. However, in thoracic endometriosis, the patches grow on or around the lungs.

Among people with endometriosis, 12% have patches of tissue in areas other than their reproductive organs. This is called extragenital endometriosis.

Thoracic endometriosis is the most common type of extragenital endometriosis.

Although it can occur on its own, more than half of people with thoracic endometriosis also have endometriosis in their pelvic area. As with these patches, the endometrium-like growths of thoracic endometriosis swell and bleed during menstruation.

Some individuals have no symptoms. If they do have any, the symptoms depend on the specific location of the endometriosis patches. Most symptoms occur during menstruation.

People with thoracic endometriosis may have the following conditions and their respective symptoms.

Catamenial pneumothorax

Pneumothorax is the medical term for a collapsed lung. This happens when air leaks into the space between the chest wall and lungs.

Catamenial pneumothorax refers to a recurrent collapsed lung within 72 hours of the start of menstruation. It occurs in 80% of people with thoracic endometriosis. In most cases, it affects the right lung.

Symptoms can include:

  • shortness of breath
  • chest pain
  • shoulder pain
  • cough

Catamenial hemothorax

Catamenial hemothorax happens when blood accumulates in the pleural space, which is the space within the lining of the lungs. Although it most commonly affects the right side, it occasionally affects the left.

The condition occurs in 14% of individuals with thoracic endometriosis, and the symptoms may resemble those of pneumothorax. They can include:

  • cough
  • shortness of breath
  • chest pain

Catamenial hemoptysis

Catamenial hemoptysis happens when there is repetitive bleeding in one or both lungs. This often happens at the same time as menstruation, as hormonal changes cause the endometriosis patches to swell and bleed.

It occurs in 5% of people with thoracic endometriosis.

Symptoms can include:

Pulmonary nodules

Pulmonary nodules are atypical growths on the lungs. They can range from half a centimeter (cm) to 3 cm in diameter.

Although they are very rare, they can occur in some people with thoracic endometriosis. Symptoms may include:

  • cough
  • shortness of breath
  • chest pain

Researchers do not fully understand what causes thoracic endometriosis, but they have several theories.

One explanation involves retrograde menstruation. This happens when menstrual blood travels backward through the fallopian tubes instead of flowing out of the body through the vagina.

It then accumulates in the abdomen.

Experts theorize that when this happens, the menstrual blood mixes with endometriosis patches of tissue. This can cause more patches farther up in the abdominal cavity, such as near the lungs.

However, doctors do not fully understand why thoracic endometriosis happens. Although many people experience retrograde menstruation, only a small percentage of them have endometriosis. Other factors may increase a person’s risk of developing the condition.

According to a 2021 study, it is hard to diagnose thoracic endometriosis because it is difficult to identify the relationship between symptoms and a person’s menstrual symptoms.

For example, a person may occasionally experience bouts of coughing, shortness of breath, and chest pain. Because these symptoms seem unrelated to menstruation, they may not even think to connect the two. This can delay diagnosis for a number of years.

If a doctor suspects thoracic endometriosis, they can diagnose the condition using:

They then compare the results of these tests performed during menstruation with those performed during the non-menses part of a person’s cycle. If the comparison shows atypical characteristics coinciding with menstruation, a doctor can diagnose the condition.

Managing the condition is the first line of treatment, but if it does not work for an individual, a doctor may perform a laparoscopy. This can both definitively diagnose the condition and treat it surgically.

The gold standard for diagnosis involves video-assisted thoracic surgery (VATS).

VATS is a minimally invasive surgery, but it does require general anesthesia and a team of specialized doctors. During the procedure, a doctor will create a small incision between the ribs and use a scope with a camera to identify and remove the endometriosis tissue.

Treatment options include medication and surgery.

Medication

Generally, the first line of treatment for endometriosis involves suppressing ovarian hormones. This suppresses the existing endometrial tissue and slows the growth of new patches.

Although medication can help, it is not a cure for the condition. Up to 60% of people using hormonal suppression therapy have a recurrence of thoracic endometriosis within 12 months.

A doctor may prescribe:

  • Gonadotropin-releasing hormone (GnRH) analogs: These drugs mimic the action of the hormone on the pituitary gland, which plays a role in estrogen production.
  • Oral contraceptives: These are medications that prevent pregnancy. They are available in pill, patch, and implant form.
  • Progestins: These are the synthetic form of the hormone progesterone.
  • Aromatase inhibitors: These medications suppress estrogen production in the ovaries and other tissues.
  • GnRH antagonists: These are medications that block the pituitary gland from responding to the GnRH hormone. This suppresses the production of certain hormones.

Surgery

Because a person with endometriosis in the thorax usually also has it on the diaphragm, treatment addresses the condition in both locations.

Surgical treatment involves removal of thoracic patches, or the patches on the lungs, with video thoracoscopy. A doctor will also remove the diaphragmatic patches, or patches on the diaphragm, with laparoscopy.

These are minimally invasive, keyhole surgeries.

After surgery, doctors can prescribe hormonal medication to slow the growth of new patches.

For those who continue to have recurrence with the combination of surgery and medication, surgical removal of the uterus, ovaries, and fallopian tubes may be necessary. Even after this more extensive surgery, an individual may still need post-surgery hormone suppression therapy.

A 2016 review states that without treatment, serious complications can occur.

If severe, catamenial pneumothorax may hinder breathing and requires immediate medical attention. Additionally, a catamenial hemothorax can cause chronic bleeding, which can be dangerous.

Treatment and regular checkups with a doctor can help manage the condition and prevent serious complications.

Thoracic endometriosis is a rare condition that happens when endometriosis patches grow on or around the lungs. This can cause shortness of breath, chest pain, cough, and in some cases, a collapsed lung.

Treatment options are medications that suppress female reproductive hormones and surgery.