PROLIFERATION OF BREAST EPITHELIAL-CELLS IN HEALTHY WOMEN DURING THE MENSTRUAL-CYCLE

OBJECTIVE: Our objective was to assess proliferation in normal breast epithelial cells from healthy women during the follicular and luteal p hases of the menstrual cycle. STUDY DESIGN: We analysed the proliferat ion marker Ki-67/MIB-1 by immunocytochemical methods in breast epithel ial cells procured through fine needle aspiration biopsy from 47 healt hy volunteers. Differences were assessed by Wilcoxon rank sum tests, a nd correlations were determined by Spearman's rank correlation coeffic ient. RESULTS: The proportion of KI-67/MIB-1-positive cells was higher in the luteal phase (2.04%) than in the follicular phase (1.66%). The values in women aged <35 years were 2.29% and 1.13%, respectively (p = 0.003). In ovulating women with two aspirates during the same menstr ual cycle the percentage of proliferating cells increased from the fol licular phase (1.3%) to the luteal phase (2.4%) (p < 0.04). Proliferat ion was positively correlated with serum progesterone levels the day o f aspiration (r = 0.34, p < 0.05). CONCLUSION: The fine needle aspirat ion biopsy technique is a valuable tool for in vivo studies of cell pr oliferation in the normal breast. Data clearly suggest a proliferative action of progesterone.