Expression of estrogen and progesterone receptors in smooth muscle metaplasia of rectovaginal endometriosis

To investigate expression of estrogen receptors (ER) and progesterone receptors (PR) in smooth muscle metaplasia (SMM) outside the endometriotic foci of rectovaginal endometriosis (RVE). One hundred and ninety-five specimens were obtained from the rectovaginal areas of the 63 patients who were underwent laparoscopic surgery for RVE. The patients were divided into 3 groups: a gonadotropin-releasing hormone (GnRH) agonist group, a non-GnRH group, including a proliferative phase group, and a secretory phase group. Expression of ER and PR in the rectovaginal tissues of RVE were determined using immunohistochemical methods. Smooth muscle metaplasia occurred in 172 specimens (88.2%), and ER and PR expression were found in the smooth muscle cells in the SMM areas outside the endometriotic foci of RVE. The expression of ER and PR in the GnRH agonist group were significantly lower than those in the non-GnRH agonist group. This is the first report demonstrating ER and PR in the smooth muscle cells in SMM outside the endometriotic foci of RVE. The ER and PR were expressed in the SMM areas, but these receptors were not recognized in fibrotic areas. We could identify the expression ratio of these receptors during each menstrual phase, with or without administered GnRH agonist.