Clinical characteristics of catamenial and non‐catamenial thoracic endometriosis‐related pneumothorax

Background and objective: A major pathogenic factor for catamenial pneumothorax is thoracic endometriosis. However, thoracic endometriosis-related pneumothorax (TERP) can develop as either catamenial or non-catamenial pneumothorax (CP). Therefore, the aim of this study was to elucidate the clinical differences between catamenial and non-catamenial TERP. Methods: The clinical and pathological data in female patients who underwent video-assisted thoracoscopic surgery at the Pneumothorax Research Center during an 8-year period were retrospectively reviewed. This study included 150 female patients with surgico-pathologically confirmed TERP. The subjects were divided into two groups, those having all of the pneumothorax episodes in the catamenial period (CP group) and those who did not (non-CP group). We compared the clinical characteristics and surgico-pathological findings between these two groups. Results: Of the 150 TERP patients, 55 (36.7%) were classified in the CP group, and 95 (63.3%) in the non-CP group. In regard to the locations of endometriosis, all TERP patients had diaphragmatic endometriosis, while pleural implantation was recognized in 34 of the 55 (61.8%) patients in the CP group and 42 of the 95 (44.2%) patients in the non-CP group (P < 0.05). Conclusions: A significant difference in the proportion of patients with pleural endometriosis was observed between catamenial and non-catamenial TERP. The ectopic sites of the endometriosis may be responsible for the timing of the pneumothorax episodes.