In outpatient clinics, we often encounter premenopausal and even some postmenopausal women with breast cancer who develop endometrial thickening after taking triamcinolone and continue to have similar presentations after being replaced with phalloidin. It seems that it is not suitable for premenopausal patients to switch to other endocrine drugs, and even if it is available, many patients cannot afford the expensive cost. What should I do if I encounter this situation? I think repeated scraping is not an option. If the medication is stopped, how long should I stop it? How do I continue taking the medication after I have stopped for a period of time and the endometrium has returned to normal levels? Is it necessary to perform depot therapy? 1. Why does TAM cause endometrial thickening? TAM has both anti-estrogen and estrogen effects. Its mechanism of action is to compete for estrogen receptors (ER) in target cells, so that the ER content in the cell plasma that can bind to estrogen decreases, thus blocking the transcriptional activation (TAF2) caused by the activation of the receptors after estrogen binds to ER, and achieving anti-estrogen effects. The anti-estrogenic effect of TAM can treat breast cancer, while its weak estrogenic effect can cause endometrial hyperplasia. Many studies have shown that long-term continuous use of TAM can lead to endometrial hyperplasia or polyps. 2. Countermeasures? With TAM, it is important to emphasize the importance of ultrasound review, and breast cancer patients with long-term TAM use must be closely tested regularly in clinical practice. The common methods to monitor the endometrium are vaginal ultrasound and diagnostic curettage. Since diagnostic curettage is difficult for every patient to accept, vaginal ultrasound is economical, convenient, non-invasive, clearly shows the endometrium and accurately measures the thickness of the endometrium, and is currently a reliable and practical method for evaluating endometrial thickness. Endometrial thickness ≥8 mm on vaginal ultrasound is the diagnostic criterion for endometrial thickening, at which point diagnostic curettage is necessary. Those less than 5 mm are not treated. Alternatively, TAM should not be used at the outset and Faradone should be used instead, which may reduce the endometrial thickening. 3.How long should I stop the medication? Personally, I think it is better to stop the medication than to actively deal with it. There are reports of progestin application for endometrial thickening, where progestin was given and then withdrawn to make the endometrium shed. 4.For some patients , drug debulking, radiotherapy or surgical debulking can be considered.