Estradiol and progesterone receptors in human breast fibroadenomas

Estradiol and progesterone receptors (ER and PR) were studied in 46 breast fibroadenomas obtained at different periods of the menstrual cycle (n = 38) or from patients under combined estrogen-progestagen contraceptive (n = 4) or substitutive progestagen treatment for progesterone insufficiency (n = 4). Cytosolic and nuclear ER (ERc and ERn) increased throughout the follicular phase and were at their maximal level in the preovulatory phase. They decreased during the luteal phase. PR levels were high in the follicular phase, especially in the cytosol (PRc). PRc then decreased while nuclear progesterone receptor (PRn) increased at the beginning of the luteal phase. Thereafter, PRc and PRn decreased and remained low during the luteal phase. PRc and PRn levels in fibroadenomas from patients under estrogen-progestagen therapy were similar to those found during the luteal phase of untreated patients. In patients receiving a substitutive progestagen treatment to correct progesterone insufficiency, PRn was markedly higher than PRc. The existence of ER and PR in breast fibroadenomas and the variations in their levels during the menstrual cycle or under hormonal treatment provide valuable information on the hormone dependency of breast fibroadenoma.