Learning Points:

– Ectopic thoracic endometrial tissue most commonly presents in young women as a right sided catamenial pneumothorax (~70%) or catamenial hemothorax (~15%).

-One needs a high clinical suspicion for diagnosis, and patients with suspected thoracic endometriosis should undergo contrast-enhanced CT scan which may show a parachymal nodule or cavity.

-Diagnosis is confirmed with direct pleural visualization with VATS procedure.

-Treatment includes endometrial implant resection and possible surgical pleurodesis. Hormonal suppression is also suggested for 6-12 months, either with GnRH analogs or OCPs.