ALTERATIONS IN STEROID-HORMONE RECEPTORS IN THE TAMOXIFEN-TREATED ENDOMETRIUM

OBJECTIVE: Our purpose was to evaluate whether tamoxifen has estrogeni c endometrial effects as defined by histologic study or alterations in steroid hormone receptor expression. STUDY DESIGN: Nineteen postmenop ausal tamoxifen-treated breast cancer patients who also had endometria l sampling were identified from files in the Department of Obstetrics and Gynecology. To examine the subgroup of 15 polyps, age-matched, non -hormonally treated patients with polyps (n = 8) or atrophic endometri a (n = 5) served as comparison groups. Proliferative (n = 3) and secre tory (n = 5) endometria served as procedural controls. Immunohistochem ical studies for steroid receptors (estrogen, progesterone) were perfo rmed. RESULTS: Glandular cell progesterone receptor was significantly increased and stromal cell estrogen receptor was significantly decreas ed in tamoxifen-treated versus atrophic endometria. Progesterone recep tor staining was not significantly different in tamoxifen-treated vers us control polyps, although staining was high in both groups. Stromal cell estrogen receptor staining was significantly reduced in tamoxifen -treated versus control polyps, although there were no histologic diff erences. Reduced stromal cell estrogen receptor and increased glandula r cell progesterone receptor staining was found in all tamoxifen-treat ed endometria regardless of the diagnosis. CONCLUSION: The tamoxifen-a ssociated changes in endometrial steroid receptors support an estrogen ic effect that is independent of histologic diagnosis and duration of use. This may contribute to the pathogenesis of tamoxifen-associated p olyps and carcinomas.