The clinicopathological study on the cause of high postoperative recurrence for catamenial pneumothorax

Purpose: Thoracic endometriosis-related pneumothorax(TERP) is caused by extra-plevic endometriosis. Diaphragmatic endometriosis is the main part of TERP, however, visceral or parietal pleural lesions have been not well-known. We aimed to clarify the clinicopathological features of thoracic endometriosis. Methods: 160 patients with TERP underwent thoracoscopic surgery at Pneumothorax Research Center between 2015 and 2019. Clinicopathological characteristics were asssessed retrospectively. Results: The median age was 41(range22-53) years. There were 159 cases of right-sided pneumothorax and one case of left-sided pneumothorax. Visceral and parietal lesions were diagnosed in 79 and 71 patients, respectively. 104 visceral pleural lesions and 101 parietal pleural lesions were diagnosed. The segment 4 of the lung and the dorsal 6th intercostal space contained the largest number of visceral pleura(66 lesions) and parietal pleural (25 lesions), respectively. Histopathological study revealed that endometic tissues existing in the outer external elastic layer in all were localized or invaded deeply. the median follow-up period in all patients was 370(range, 6-18249) days. The one and two year postoperative recurrence rates were 13.8% and 19.3%, respectively in Kaplan-Meire curve. Conclusions: Visceral endometriotic lesions are disseminated from diaphragmatic endometriosis and infiltrate into the pleura. Careful observation of the specific sites, such as the visceral pleura of S2, S4, and S6 of the lung, and the parietal pleura between 6th and 8th intercostal space should be necessary in thoracoscopic surgery in order to reduce postoperative recurrence.