PROLIFERATION OF THE BREAST EPITHELIUM IN RELATION TO MENSTRUAL-CYCLEPHASE, HORMONAL USE, AND REPRODUCTIVE FACTORS

The proliferative rate in normal breast epithelium from 58 women under going reduction mammoplastics was studied using the formalin resistant antibody Ki-S5, and related to age at operation, menstrual cycle phas e, family history of breast cancer, height and weight, parity, and hor monal use. The breast tissue from women operated on in the luteal mens trual cycle phase (day 15-28 among oral contraceptive (OC) users) had significantly higher proliferative rate than breast tissue removed fro m women in the follicular phase (day 1-14) (p = 0.01). Among women pre sently exposed to hormones, those with a positive family history of br east cancer among first and second degree relatives had significantly higher values than cases without such history (p = 0.02). Weight was n ot significantly related to proliferation rate, while a short height w as associated with a significantly higher proliferation rate (p = 0.04 ). Women who used OCs before the first full-term pregnancy (FFTP) had a significantly higher proliferation rate compared with never users or late users (p = 0.04). No significant difference was seen between par ous versus nulliparous women.The results from the univariate analysis persisted in multivariate models. An especially high proliferation rat e was seen in young women with both a positive family history and pres ent hormonal use (p = 0.001). Overall, it was found that young women h ad a non-significantly higher proliferation rate than older women (p = 0.10). Due to small sample size, these results must be regarded as pr eliminary, especially in the subgroup analyses.