Schematic illustration of breaking of the visceral pleural structure in endometriosis.

Endometriotic tissue migrating in the thoracic space may be located on the surface of the visceral pleura (A). Subsequently, proliferation and breakdown of the endometriotic tissue may occur during menstruation cycles on the surface of pleura as the same fashion of uterus. It may lead to bleeding, tissue repair, and inflammation of the endometriotic lesion involving the surrounding pleural tissue, suggesting stepwise breaking of the pleural structure (mesothelial, sub-mesothelial, external elastic, subpleural, and internal elastic layer) (B-D).