Persistent pneumothorax during pregnancy revealing histologically confirmed thoracic endometriosis.

Thoracic endometriosis syndrome (TES) is the leading cause of catamenial pneumothorax but is rarely considered during pregnancy because ovulation and menstruation are physiologically suppressed. Consequently, persistent pneumothorax in pregnancy is commonly attributed to primary spontaneous pneumothorax, potentially delaying definitive diagnosis and treatment. We report a 31-year-old primigravida at 27 weeks' gestation who presented with persistent right-sided pneumothorax despite tube thoracostomy. She had a history of recurrent spontaneous pneumothorax and pelvic endometriosis. Following multidisciplinary evaluation, the patient underwent video-assisted thoracoscopic surgery with wedge resection of the right middle lobe and partial diaphragmatic resection with primary repair. Histopathological examination demonstrated endometrial glands and stroma involving the pulmonary parenchyma, pulmonary bulla, and diaphragm, with positive estrogen receptor and CD10 immunostaining, confirming TES. The postoperative course was uneventful, and the patient subsequently delivered a healthy 3.2-kg female infant at 40 weeks' gestation without maternal or neonatal complications. This case demonstrates that pregnancy does not exclude TES and highlights the importance of maintaining clinical suspicion in pregnant women with recurrent or persistent right-sided pneumothorax. Early multidisciplinary surgical management can safely achieve definitive diagnosis and treatment while optimizing both maternal and fetal outcomes.