Tamoxifen is an estrogen modulator, which has an inhibitory effect on breast tumors and is often used as a postoperative adjuvant for breast cancer. Tamoxifen generally plays a role in promoting the proliferation of the endometrium, so during the treatment of breast cancer with tamoxifen, the endometrium should be closely observed, and if there is irregular vaginal bleeding, or thickening of the endometrium, it is necessary to scrape the uterus for examination in a timely manner, except for endometriosis, or even endometrial cancer. Tamoxifen is also sometimes used as one of the therapeutic drugs for ovarian malignant tumors. For advanced recurrent ovarian cancer, in addition to chemotherapy, sometimes tamoxifen or high-dose progesterone can be given to inhibit tumor proliferation with certain curative effect.