Tamoxifen use and endometrial lesions: hysteroscopic, histological, and immunohistochemical findings in postmenopausal women with breast cancer

Objective: To evaluate immunohistochemical, hysteroscopic, and histological findings in postmenopausal women taking tamoxifen for breast cancer. Methods: Forty postmenopausal women taking 20 mg/day tamoxifen for breast cancer underwent hysteroscopy and endometrial biopsy from January 2000 to December 2003. Medical records and paraffin blocks were analyzed retrospectively, and Ki-67, estrogen receptors (ERs), and progesterone receptors were measured using all immunohistochemical technique. Results: The mean +/- SD age of the women was 59 +/- 14 years at hysteroscopy (95% CI, 54.2-63.7) and 45.1 +/- 7 years at menopause (95% CI, 42.6-47.6). Mean +/- SD duration of tamoxifen therapy was 27.3 +/- 16.5 months (95% CI, 22.0-32.5). Hysteroscopies were performed because of abnormal sonographic findings in 60% of the women and postmenopausal bleeding in 40%. The most common hysteroscopic and histological findings were endometrial polyps (32.5%) and atrophic endometria (22.5%). Immunohistochemistry showed that 85% of the women were progesterone receptor positive, 75% were ER positive, and 50% were Ki-67 positive. Endometrial polyps and polyps associated with atrophic endometrium were ER positive (P = 0.019). Results that were ER negative were more frequent in atrophic endometria (P = 0.01). The longer the time since menopause, the lower the Ki-67 expression in the endometrium was (P = 0.03). Ki-67 expression was greater in the endometrium of younger postmenopausal women (P = 0.01). Conclusions: The expression of steroid receptors in the endometrium was high in our series. All cases of endometrial polyps were ER positive. Estrogen receptors may play a major role in the development of endometrial polyps in postmenopausal women taking tamoxifen. Although most histological findings were benign, 22.5% were atrophic.