EPITHELIAL PROLIFERATION AND HORMONE-RECEPTOR STATUS IN THE NORMAL POST MENOPAUSAL BREAST AND THE EFFECTS OF HORMONE REPLACEMENT THERAPY

The proliferation rate las assessed by Ki67 expression) and expression of oestrogen-regulated progesterone receptor (PR) was studied in norm al post-menopausal breast epithelium. Normal breast epithelium from pa tients receiving hormone replacement therapy (HRT) at the time of surg ery containing either oestrogen alone (E-2) or oestrogen and progester one combined activities (E-2 + P) was also studied, as HRT has been li nked to an increased breast cancer risk. Samples of breast tissue, con taining normal epithelium, from 185 patients undergoing surgery for be nign or malignant disease were immunocytochemically stained for PR and Ki67. The percentage of labelled cells was expressed as the labelling index (LI). The median Ki67 LI in normal post-menopausal breast epith elium was 0.19 and median PR LI was 4.75, and both were unaffected by patient age, duration of menopause or if the tissue sample originated from a breast with benign or malignant disease. Proliferation did not alter significantly in patients taking HRT (P = 0.61); however, PR exp ression was up-regulated in both E-2 and E-2 + P users (P = 0.01). The dose and duration of HRT had no effect on either parameter. A possibl e attenuation of sensitivity to oestradiol-induced proliferation but n ot to PR expression occurs in the post-menopausal breast.