Evaluation of Proliferative Activity in the Mammary Epithelium Adjacent to Fibroadenoma in Women Treated with Tamoxifen - Revista Brasileira de Ginecologia e Obstetrícia

Purpose: to study the monoclonal antibody MIB-1 in the normal breast epithelium adjacent to a fibroadenoma in women in the luteal phase of the menstrual cycle treated with tamoxifen. Patients and methods: the proliferative activity of the mammary epithelium adjacent to the fibroadenoma was studied by immunohistochemistry based on immunoexpression of the monoclonal antibody MIB-1. The study was randomized and double blind and was conducted on 44 women with fibroadenomas, divided into 3 groups: A (n = 16; placebo), B (n = 15; tamoxifen, 10 mg), and C (n = 13; tamoxifen, 20 mg). Tamoxifen was administered for 22 days starting on the 2nd day of the menstrual cycle and a biopsy was taken on the 23rd day. Results: the mean percentage of stained nuclei per 1000 cells was 9.2 in group A, 4.5 in group B, and 3.2 in group C. Fisher’s test revealed that tamoxifen significantly reduced the immunoexpression of MIB-1 at the doses of 10 and 20 mg compared to the placebo group (p<0.0001), with no significant differences between doses in terms of proliferative activity (p = 0.21). Conclusion: we conclude that tamoxifen significantly reduced the proliferative activity of the mammary epithelium at the doses of 10 and 20 mg/day.