Catamenial pneumothorax associated with endometriosis of the diaphragm

A case of catamenial pneumothorax is documented. At thoracotomy, there was a small black mass measuring 10 x 6 mm associated with surrounding petechiae on the top of the dome of the right diaphragm. Microscopic examination revealed the presence of endometrial tissue. We could not find any diaphragmatic defect in this case.