Altered expression of steroid receptors in uterine leiomyoma and myometrium: An immunohistochemical evaluation

The origin of uterine leiomyomas, hormone-sensitive tumors, is unknown. In an effort to determine whether the growth of these leiomyomas is related to an alteration in the level of steroid receptors, we analysed the expression of estrogen receptors (ER), progesterone receptors (PR), and androgen receptors (AR) within leiomyoma and myometrium by immunohistochemistry using computerized image analysis to quantify our results. Leiomyoma and adjacent myometrium from 12 premenopausal women who had undergone hysterectomy or myomectomy for symptomatic uterine leiomyoma served as the study samples. Myometrium from 14 premenopausal women with a non-leiomyomatous uteri who underwent hysterectomy served as controls. Histograms of nuclear receptor immunostaining were scored in a semiquantitative fashion. ER expression was significantly greater in leiomyomas than in the adjacent myometrium (P = 0.0004) but did not differ from control myometrium. There was significantly less AR expression in the myometrium of myomatous uteri than in both adjacent leiomyomas and control myometrium (P = 0.006 and P = 0.048, respectively). In contrast, PR expression was not significantly different between leiomyomas and either group of myometrium. ER expression fluctuated with the menstrual cycle within myomas but did not change appreciably within the myometrium of the study and control groups. The demonstration of lower AR expression in the myometrium of uteri with leiomyomas than in those without suggests that an inherent steroid receptor defect may contribute to the pathogenesis of leiomyomas, and that future studies should be directed toward the involvement of androgens in the regulation of the growth and development of the uterine myometrium.