Triamcinolone is a non-steroidal anti-estrogen drug. It is one of the commonly used drugs in the treatment of breast cancer and lobular hyperplasia of the breast with endocrine therapy. However, clinical practice has proven that treating breast cancer with triamcinolone acetonide can cause ovarian cysts. Ovarian cysts can be divided into benign ovarian cysts and malignant ovarian cysts. The consequences of having a malignant ovarian cyst are self-explanatory. Even a benign simple ovarian cyst, when it is too large, can lead to ovarian cyst torsion and requires surgical treatment. Studies have demonstrated that the incidence of ovarian cysts caused by breast cancer treated with triamcinolone acetonide is 19.35%. The cause of its development is still unknown. It is generally believed that: the chemical structure of triamcinolone is similar to that of clomiphene. They both have anti-estrogenic effects and can compete with estradiol for receptors, which will reduce the level of estradiol in the body and increase the secretion of hypothalamic gonadotropin-releasing hormone (GnRH). The increase in gonadotropin-releasing hormone, in turn, raises the blood levels of follicle stimulating hormone (FSH) and luteinizing hormone (LH). When the ovaries are overstimulated by these two excess hormones, ovarian cysts can result. In addition, triamcinolone can also act directly on the granulosa cells of the ovary, which, mediated by insulin growth factor, can cause ovarian cysts to form as a result of follicular overgrowth. Ovarian cysts caused by breast cancer treated with triamcinolone occur mainly in patients who are not menopausal or have been menopausal for less than one year. In particular, the highest incidence of ovarian cysts, up to 63.2%, occurs in women with regular menstrual periods when triamcinolone is applied. In contrast, ovarian cysts do not occur in patients who have been menopausal for more than one year when triamcinolone is applied. Triamcinolone is a very effective adjuvant drug in the treatment of breast cancer and lobular hyperplasia. However, two points should be noted when applying it: 1. Patients should have a thorough gynecological examination before using the drug, and if abnormal enlargement of the ovaries is found, triamcinolone can be used without or withheld. 2. Patients who apply triamcinolone acetonide for breast disease should have their ovaries examined frequently during the medication period. If ovarian cysts are found, a consultation with an experienced specialist should be made to determine the nature of the ovarian cysts to see if it is a functional ovarian cyst or ovarian tumor or an ovarian metastasis from breast cancer. If the patient’s ovarian cyst is unicompartmental and its diameter is less than 5 cm, then triamcinolone acetonide can be continued. If the patient’s ovarian cyst is multi-housed, or if it is too large in diameter, discontinue triamcinolone acetonide. If the cyst does not shrink or continues to increase in size 2-3 months after discontinuation of triamcinolone, surgical treatment should be performed.