Alterations in steroid hormone receptors in the tamoxifen-treated endometrium

Our purpose was to evaluate whether tamoxifen has estrogenic endometrial effects as defined by histologic study or alterations in steroid hormone receptor expression.

Nineteen postmenopausal tamoxifen-treated breast cancer patients who also had endometrial 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 endometria (n = 5) served as comparison groups. Proliferative (n = 3) and secretory (n = 5) endometria served as procedural controls. Immunohistochemical studies for steroid receptors (estrogen, progesterone) were performed.

Glandular cell progesterone receptor was significantly increased and stromal cell estrogen receptor was significantly decreased in tamoxifen-treated versus atrophic endometria. Progesterone receptor staining was not significantly different in tamoxifen-treated versus 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 differences. Reduced stromal cell estrogen receptor and increased glandular cell progesterone receptor staining was found in all tamoxifen-treated endometria regardless of the diagnosis.

The tamoxifen-associated changes in endometrial steroid receptors support an estrogenic effect that is independent of histologic diagnosis and duration of use. This may contribute to the pathogenesis of tamoxifen-associated polyps and carcinomas.