The early response of the postmenopausal endometrium to tamoxifen: expression of estrogen receptors, progesterone receptors, and Ki-67 antigen.

Author(s): Tregon ML, Blumel JE, Tarin JJ, Cano A

Affiliation(s): Department of Pediatrics, Obstetrics and Gynecology, Facultad de Medicina, Universidad de Valencia, Valencia, Spain.

Publication date & source: 2003-03, Menopause., 10(2):154-9.

Publication type: Clinical Trial; Randomized Controlled Trial

OBJECTIVE: To enlighten the early response of endometrium to tamoxifen by assessing the expression of estrogen receptors, progesterone receptors, Ki-67, and the histological response in endometria from normal postmenopausal women treated for 21 days with tamoxifen. DESIGN: A total of 40 women, scheduled to undergo vaginal hysterectomy because of uterine prolapse, were randomly assigned to the tamoxifen group (20 mg/day; 20 women) or the control group (20 women). Samples were obtained from the upper and the lower thirds of the uterine cavity. Standard immunohistochemical staining of estrogen and progesterone receptors and of Ki-67 was performed on frozen sections. Staining was assessed using semiquantitative immunoreactivity scores. RESULTS: Simple endometrial hyperplasia was diagnosed in 18 of the 20 samples exposed to tamoxifen compared with only 2 of the 20 controls ( P< 0.0005). Staining was increased in both the epithelium and stroma in the tamoxifen samples, a difference that was significant for estrogen receptors in glandular epithelium (180 +/- 80 v 110 +/- 110; P< 0.05). Also, Ki-67 antigen was expressed more frequently in both glandular epithelium ( P< 0.05) and stroma ( P< 0.05) in the tamoxifen samples. CONCLUSIONS: Tamoxifen rapidly up-regulated the cell proliferation markers, an effect that was associated with enhanced growth as confirmed by increased expression of estrogen receptors and Ki-67, in addition to a high incidence of glandular hyperplasia.