Thoracic endometriosis

Her chest radiography demonstrated pneumothorax; endometrial deposits were identified during thoracoscopy implicating catamenial pneumothorax as the cause of her chest pain.

⁣Endometriosis is the condition wherein endometrial tissue is present outside of the uterine cavity. It is encountered most commonly in pelvic structures such as the ovary, uterine ligaments, pelvic peritoneum, cervix, labia, and vagina.⁣
⁣
⏩ Thoracic endometriosis syndrome (TES) is the presence of endometrial tissue in or around the lung. TES consists of 4 distinct clinical entities: catamenial pneumothorax (CP), catamenial hemothorax (CHx), hemoptysis, and pulmonary nodules. Although endometriosis in general can affect up to 15% of women in their reproductive years, TES remains an exceedingly rare condition.⁣
⁣
Described as early as 1912 by Hart, endometriosis is documented as causing pulmonary lesions consisting of endometrial glands and stroma. In 1938, Schwartz described a woman with inguinal node endometriosis with hemoptysis with a “lung tumor” that bled with every menstrual cycle. Since then, endometriosis has been documented in the lung, bronchi, pleura, and diaphragm.⁣
⁣
⏩ In the past 100 years, there has been improved understanding of the prevalence, clinical manifestations, diagnosis, and treatment of TES. The two largest retrospective studies in this period noted the peak incidence of TES occurs between ages 30 to 35 years, with CP the most common presentation of TES.⁣
⁣
It remains unclear how endometrial tissue migrates to the thoracic cavity. In 1927, the concept of retrograde menstruation, or the reflux of endometrial tissue from the uterus to the peritoneum via the fallopian tubes, was introduced as the etiology of peritoneal endometrial implants.⁣
⁣
Once in the peritoneal cavity, endometrial tissue was thought to travel to the thorax via diaphragmatic fenestrations.⁣
⁣
 These fenestrations were believed to be either congenital or the result of direct erosion by endometrial implants and could be as large as four inches in diameter. ⁣
⁣
Alternative theories for the presence of endometrial tissue in the lungs have been presented, including coelomic metaplasia, or the transformation of peritoneal/pleural epithelium into endometrial tissue under the influence of physiologic stimuli.⁣
⁣

This theory explains the presence of endometrial tissue in patients without a uterus including men on prolonged estrogen therapy.⁣
⁣
However, it fails to explain the right-sided thorax predominance seen in most TES cases.⁣
⁣
An additional theory is that endometrial transplantation occurs through lymphatic/vascular microembolization, explaining the presence of both intrapulmonary and other extra-uterine sites of implantation.