Tamoxifen, a selective estrogen receptor modulator, is the standard adjuvant therapy for hormone receptor-positive breast cancer. Although it acts as an estrogen receptor antagonist in breast tissue, it may exert agonistic effects on the endometrium, increasing the risk of endometrial polyps, hyperplasia, and malignancy. We report a rare case of a 51-year-old woman who developed both an endometrial polyp and a vaginal superficial myofibroblastoma after approximately 4 years of tamoxifen therapy. This case emphasizes the importance of long-term gynecologic surveillance in patients receiving tamoxifen treatment.
