Immunohistochemical analysis of thoracic endometriosis.

Thoracic endometriosis is a rare disease responsible for catamenial pneumothorax. The immunohistochemical features of thoracic endometriosis are not well understood. An immunohistochemical examination of 84 diaphragmatic specimens of catamenial pneumothorax using antibodies against estrogen receptor (ER), progesterone receptor (PgR), CD10 and smooth muscle actin (SMA) was conducted. The endometrial tissue was small, and focally located around the chasm of the tendon on the side of the thoracic cavity. Endometrial stroma were detected in 84/84 (100%) of the specimens, endometrial glands were detected in 21/84 (25%) and smooth muscle was detected in 1/84 (1.2%). The endometrial stroma exhibited positive staining for ER in 74/84 (88.1%) of the specimens, PgR in 84/84 (100%), CD10 in 74/84 (88.1%) and SMA in 46/84 (54.8%). Because thoracic endometriosis is small in size, and only 25% of the resected tissue specimens were accompanied with the endometrial gland, an immunohistochemical analysis can be useful for their detection. The fact that over half of the thoracic endometrial stroma showed positive staining for SMA, and the existence of thoracic endometriosis accompanied by smooth muscle, indicated that some part of the thoracic endometriosis may have the ability to differentiate into smooth muscle, although further studies are needed to confirm this hypothesis.