Thoracic endometriosis: clinicopathologic updates and issues about 18 cases from a tertiary referring center

Thoracic endometriosis is defined as the ectopic presence of endometrial glands and stroma in lung or pleura and constitutes an uncommon cause of spontaneous pneumothorax in nonsmoker women in childbearing age. From 2000 to 2014, 18 (7.3%) women of 246 had a histologically proven endometriosis-related pneumothorax. The examination of thoracic samples was performed on formalin-fixed, paraffin-embedded hematoxylin and eosin–stained slides. Immunohistochemistry was carried out on all samples. The pathologic findings included endometriosis foci appearing as a triad of endometrial glands, stroma, and hemosiderin-laden macrophages in 8 patients. In the remaining 10 patients, minute nests of endometrial stroma were recognized at histologic examination and immunohistochemistry. One patient displayed diaphragmatic endometriosis and pulmonary lymphangioleiomyomatosis. Thoracic endometriosis is an uncommon cause of recurrent pneumothorax necessitating histologic confirmation. The histologic diagnosis of endometriosis may be challenging on small pleural or lung biopsies because endometriosis mostly appears as minute nests of endometrial stromal cells. Here, we present our experience on thoracic endometriosis: considering frequent interpretation difficulties of biopsy samples, we propose a multidisciplinary diagnostic algorithm.