Estrogenic Activity of Tamoxifen on the Epithelium of Normal Mammary and Fibroadenoma in the Luteal Phase of the Menstrual Cycle

Abstract

: Tamoxifen, an antiestrogenic drug used in adjuvant therapy in breast cancer, is in need of further studies to determine its effectiveness for treatment of benign disease and in cancer prevention. This study examines the effect of tamoxifen on the epithelium of fibroadenomas and its respective normal adjacent parenchyma by quantitative analysis of lysosomes. Tamoxifen was administered to 18 patients during the luteal phase of the menstrual cycle, thus reducing interference with the secretory activity of the corpus luteum. Biopsies were obtained from adjacent tissue and fibroadenomas were obtained during their surgical resection in 35 premenopausal women. Ages ranged from 15 to 37 years old and all patients had a regular cycle for at least 6 months. The patients were divided randomly into two groups: 17 from group A (control) and 18 from group B (tamoxifen) treated with tamoxifen, 20 mg/day between the 13th and 22nd day of the cycle. The tissue fragments were prepared according to the Gomori's cytochemical method using the acid phosphatase reaction. Lysosome counts were carried out with a light microscope and grid lenses at high magnification and the results were analyzed with the Mann–Whitney test. The epithelium of fibroadenoma had significantly more lysosomes than those seen in the epithelium of adjacent mammary parenchyma. The patients who received tamoxifen showed a statistically significant decrease in the number of lysosomes in the epithelium of mammary parenchyma and fibroadenoma, demonstrating an antiestrogenic effect.