Catamenial pneumothorax with histologically proven diaphragmatic endometriosis successfully managed by combined surgical resection and hormonal therapy: A four-year recurrence-free case

A 43-year-old woman presented to the emergency department with acute right-sided chest pain and dyspnea. She was hemodynamically stable with a blood pressure of 118/70 mmHg, pulse rate of 82 beats/min, oxygen saturation of 94 % on room air, and body temperature of 36.6 °C. Chest radiography revealed a massive right-sided pneumothorax with complete collapse of the right lung ( Fig. 1 ). A chest tube was inserted with adequate re-expansion. The episode coincided with her menstrual period, and she reported a history of recurrent right pneumothoraces that correlated with menstruation, raising suspicion for catamenial pneumothorax. Laboratory findings showed an elevated CA125 level of 53 U/mL (reference <35 U/mL). Thoracoscopic surgery was performed. A bulla was identified in the superior segment of the right lower lobe ( Fig. 2 ) and resected by wedge resection. On the diaphragmatic surface, brownish fenestrations and nodules were observed ( Fig. 3 ) and partially resected. Histopathological examination of the resected lung bulla showed no evidence of ectopic endometrial tissue. In contrast, histological examination of the diaphragmatic specimen (H&E, × 10; Fig. 4 ) revealed ectopic endometrial glandular structures lined by tall columnar epithelium without atypia, consistent with endometrial-type glands and stroma. Immunohistochemistry for estrogen receptor (ER, × 20; Fig. 5 ) demonstrated strong nuclear positivity in the glandular epithelium, confirming the diagnosis of ectopic endometriosis. The postoperative course was uneventful, and the patient was discharged on postoperative day 3. Two weeks later, CA125 levels increased to 94 U/mL. Given the likelihood of hormonal activity, combined hormonal therapy was initiated by the gynecology department using six courses of gonadotropin-releasing hormone agonist (leuprorelin) followed by oral dienogest (1 mg daily). Serum CA125 subsequently normalized, and no recurrence has been observed for four years postoperatively. Fig. 1 Chest X-ray showing a massive right pneumothorax with complete collapse of the right lung. Fig. 1 Fig. 2 Thoracoscopic view showing a bulla in the superior segment of the right lower lobe (arrow). Fig. 2 Fig. 3 Thoracoscopic image showing brownish diaphragmatic fenestrations and nodules (arrowheads). Fig. 3 Fig. 4 Histopathological findings (H&E, × 10) showing ectopic endometrial glandular structures lined by tall columnar epithelium without atypia. Fig. 4 Fig. 5 Immunohistochemistry for estrogen receptor (ER, × 20) showing strong nuclear positivity in glandular epithelial cells. Fig. 5 Chest X-ray showing a massive right pneumothorax with complete collapse of the right lung. Thoracoscopic view showing a bulla in the superior segment of the right lower lobe (arrow). Thoracoscopic image showing brownish diaphragmatic fenestrations and nodules (arrowheads). Histopathological findings (H&E, × 10) showing ectopic endometrial glandular structures lined by tall columnar epithelium without atypia. Immunohistochemistry for estrogen receptor (ER, × 20) showing strong nuclear positivity in glandular epithelial cells.

Eitetsu Koh: Writing – review & editing, Writing – original draft, Visualization, Validation, Software, Resources, Project administration, Methodology, Investigation, Funding acquisition, Formal analysis, Data curation, Conceptualization. Tadao Nakazawa: Supervision. Yoshiyuki Nakajima: Supervision.

Written informed consent was obtained from the patient for publication of this case report and accompanying images.

This case highlights the importance of recognizing catamenial pneumothorax as a potential cause of recurrent spontaneous pneumothorax in women. Definitive diagnosis can be achieved through histologic confirmation of diaphragmatic endometriosis. Combined surgical and hormonal therapy is effective for long-term recurrence prevention.

Catamenial pneumothorax accounts for approximately 3–6 % of spontaneous pneumothoraces in women of reproductive age. The right-sided predominance has been attributed to transdiaphragmatic passage of endometrial tissue through small fenestrations and the presence of “protective effects of the liver on the right diaphragm, whereas such a barrier is absent on the left side. Thoracic endometriosis may also present as catamenial hemothorax or catamenial hemoptysis, which should be considered in the differential diagnosis of women presenting with cyclical hemothorax or pulmonary hemorrhage. The pathogenesis of CP likely involves multiple mechanisms, including retrograde menstruation, migration of endometrial cells through diaphragmatic defects, hematogenous or lymphatic spread, and prostaglandin-mediated alveolar rupture. In our case, the absence of endometrial tissue in the lung and the presence of diaphragmatic endometriosis suggest that transdiaphragmatic migration was the predominant mechanism. Surgical management typically includes resection of visible endometriotic lesions, repair or resection of diaphragmatic defects, and treatment of associated pulmonary lesions such as bullae or blebs. In selected recurrent or refractory cases, chemical or mechanical pleurodesis may also be considered as an adjunct to prevent recurrence. Our patient underwent surgical resection followed by hormonal therapy, which effectively prevented recurrence. The postoperative increase in CA125 that normalized after hormonal therapy suggests persistent microscopic endometriotic activity, supporting the necessity of combined therapy rather than surgery alone.

Catamenial pneumothorax is the most common manifestation of thoracic endometriosis syndrome, typically occurring within 72 hours of menstruation. Multiple mechanisms have been proposed, including retrograde menstruation with transdiaphragmatic passage of endometrial tissue, microembolization, and hormonal influences on pleural surfaces. Histologic confirmation of diaphragmatic endometriosis is uncommon, as many cases are diagnosed intraoperatively by endoscopic visualization without tissue confirmation. Here, we report a rare case with histologically proven diaphragmatic endometriosis.

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.