A 58-year-old postmenopausal woman taking adjuvant tamoxifen for ER-positive breast cancer presents with new vaginal bleeding. Endometrial sampling is arranged because tamoxifen:

• A Directly damages endometrial glands through a cytotoxic metabolite
• B Acts as a pure oestrogen antagonist at all tissues including the endometrium
• C Stimulates residual ovarian follicles even after menopause
• D Exerts partial oestrogen agonist activity on the endometrium, increasing hyperplasia and carcinoma risk ✓

Explanation

Tamoxifen is a selective oestrogen receptor modulator: antagonistic in breast tissue but agonistic in endometrium, bone and liver. Its endometrial agonism raises the incidence of polyps, hyperplasia and adenocarcinoma, so postmenopausal bleeding on tamoxifen always warrants sampling. It does not reactivate ovaries after menopause, and its toxicity profile is hormonal modulation rather than direct cytotoxic injury.

Reference: Williams Gynecology, 4th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.