We report on an unusual endometrial polyp in a postmenopausal woman taking tamoxifen for 7 years after surgical resection of a breast carcinoma. A 63-year-old woman with endometrial thickening was submitted to hysteroscopy with biopsy, which revealed a polyp with a sex cord-like pattern. The hysterectomy specimen showed florid adenomyosis, and in the background, there were rare sex cord-like foci. Immunohistochemistry can be useful in differentiating sex cord-like elements from metastatic breast cancer to endometrium. This is, to our knowledge, the first observation in literature correlated to tamoxifen intake.25170-2