[Estrogen receptor kinetics in benign and malignant diseases of the breast and their clinical implication]

Estrogen and progesterone binding capacities in the breast tissues were determined. Unoccupied cytoplasmic estrogen receptor (ERc) levels in 19(37%) out of 52 patients with breast cancer revealed more than 30fmol/mg protein. None of tissues from the benign breast diseases contained higher unoccupied ERc than 30fmol/mg protein. There was no significant difference between the level of unoccupied ERc in the patients with fibroadenoma and that in those with mastopathy. Occupied ERc levels were significantly lower than unoccupied ERc in the breast cancer, but the difference was not observed in benign breast diseases. Occupied nuclear estrogen receptor (ERn) levels were significantly lower than unoccupied ERn only in the premenopausal patients with breast cancer, but no significant difference was observed in the patients with benign breast diseases. The level of progesterone receptor (PgR) was low in both breast cancer and benign breast diseases. Serum estradiol (E2) and progesterone (PRG) concentrations were assayed on patients with the benign breast diseases who had regular menstrual cycles. Significant negative correlations were recognized between the levels of PRG and PgR at a luteal phase, but not between E2 and unoccupied ERc. Four (33%) out of 12 patients with recurrent breast cancer responded to the endocrine therapy. In three (75%) of the four responded patients unoccupied ERc level of the cancer tissue was more than 30fmol/mg protein.