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Abnormal uterine bleeding and uterine pathology in women on tamoxifen therapy

Steven R Goldstein, MD
Jamie N Bakkum-Gamez, MD
Section Editors
Robert L Barbieri, MD
Barbara Goff, MD
Harold Burstein, MD, PhD
Deputy Editor
Sandy J Falk, MD, FACOG


Tamoxifen is a nonsteroidal selective estrogen receptor modulator that is used primarily for adjuvant treatment of estrogen receptor-positive breast cancer in premenopausal women, and in some postmenopausal women [1]. It is also used for chemoprevention in women at increased risk for breast cancer.

Tamoxifen is associated with increased risks of uterine pathology, including endometrial polyps, endometrial carcinoma and hyperplasia, uterine sarcoma, and uterine carcinosarcoma.

Uterine pathology in women on tamoxifen is reviewed here. Use of tamoxifen for breast cancer therapy or breast cancer prevention and management of other adverse effects associated with tamoxifen are reviewed separately. (See "Adjuvant endocrine therapy for non-metastatic, hormone receptor-positive breast cancer" and "Selective estrogen receptor modulators and aromatase inhibitors for breast cancer prevention" and "Managing the side effects of tamoxifen".)


Mechanism of action — Tamoxifen is a competitive inhibitor of estrogen, binding to the estrogen receptor in the breast, which blocks tumor proliferation [2,3]. However, tamoxifen has a complex mechanism of action against tissues. While it is anti-estrogenic in the breast, it can be either an estrogen antagonist or agonist at different sites of the female reproductive tract.

Endometrial and menstrual effects — Tamoxifen is a mixed estrogen antagonist and agonist (referred to as a selective estrogen receptor modulator [SERM]).

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Literature review current through: Nov 2017. | This topic last updated: Mar 06, 2017.
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