Endometriosis of the lung, also called thoracic endometriosis syndrome, is an uncommon disease in which functioning endometrial tissue is present in the lung parenchyma, pleura, or diaphragm. This disease primarily occurs in young females of reproductive age. Thoracic involvement is the most common location for endometriosis outside of the pelvis. Its incidence is unknown, but thoracic endometriosis is reported in <1% of women undergoing pelvic surgery for suspected or diagnosed endometriosis.

Common presenting symptoms include pneumothorax, hemothorax, or hemoptysis, with recurrent episodes aligning with the patient's menstrual cycle. Of note, symptoms may not be associated with the patient's menstrual cycle in a minority of cases, particularly with pneumothorax.

The pathogenesis of endometrial tissue development in the thoracic cavity is still unclear. Most women with endometriosis in the lung also have a history of pelvic endometriosis. While formerly considered very rare, it may be an underdiagnosed cause of spontaneous pneumothorax in women. Rarely, thoracic endometriosis may present with solitary or multiple pulmonary nodules.

Treatment of endometriosis of the lung is similar to treatment in the pelvis. Oral contraceptive pills or gonadotropin-releasing hormone (GnRH) agonists may relieve symptoms. Surgical resection of endometrial implants through video-assisted thoracoscopic surgery (VATS) is also effective.

Related topic: Cutaneous endometriosis