PURPOSE: to quantitatively analyze the immunoreaction of monoclonal antibody Ki-67 in the mammary epithelium adjacent to fibroadenoma of premenopausal women treated with tamoxifen, for 50 days, at doses of 5, 10 and 20 mg/day. METHODS: we studied, prospectively, the effects of tamoxifen administered for 50 days, at doses of 5, 10 e 20 mg/day, by the immunoreaction of the Ki-67 (clone Ki-S5) monoclonal antibody on mammary epithelium adjacent to fibroadenoma in premenopausal women. We studied 58 patients in a double-blind trial who were divided into four groups: Group A (n=13; placebo), Group B (n=16; 5 mg/day tamoxifen), Group C (n=14; 10 mg/day) and Group D (n=15; 20 mg/day). All patients received the medication from the first day on of the menstrual cycle and biopsy was performed on the last day of the treatment. Cells stained and not stained by the immunoreagent were counted by optical microscopy (400X) with a digital image capturing system and image analysis. RESULTS: the average percentage of stained nuclei was calculated for all groups: Group A was 2.0 with a standard error (SE) of 0.3. In Group B it was 0.7 (SE=0.2); in Group C it was 0.4 (SE=0,2) and in Group D it was 0.1 (SE=0). Statistical analysis showed significant reductions between the groups (p<0.001), and Tukey's pairwise comparison test confirmed that there was a significant increase in the immunoreaction of the monoclonal Ki-67 antibody in groups B, C and D. CONCLUSIONS: tamoxifen, administered at doses of 5, 10 and 20 mg/day for 50 days, significantly reduced the immunoreaction of monoclonal Ki-67 in the mammary epithelium of premenopausal patients and there was no significant difference between the groups that received 5, 10 and 20 mg/day tamoxifen.
Tamoxifen; Immunohistochemistry; Breast; Breast; Fibroadenoma
