There are many causes of nipple retraction in women, such as dysplasia, trauma or surgery, dilated milk ducts, periductal mastitis, breast cancer, etc. The diagnosis is based on the actual situation. I. Non-disease factors: 1. Dysplasia: congenital nipple retraction is mainly caused by too short breast ducts, poorly developed smooth muscle under the nipple and lack of relevant supporting tissue under the nipple; 2. Trauma or surgery: damage to the breast ducts during trauma may lead to nipple retraction. In addition, the muscle tissue under the breast ducts may be damaged after breast surgery, which may also lead to nipple invagination. The reason for this is that it is not possible to get a good idea of what to do with the ducts. The cause may be pathogenic infection or non-specific inflammatory manifestations; 3. Breast cancer: breast cancer is also an important cause of nipple invagination, and most women may experience nipple bleeding or breast lumps, the cause of which is related to genetics, sex hormones and genetic mutations. There are many causes of nipple indentation, and for non-disease causes it can usually be treated without treatment or medical aesthetics. If it is a disease cause, it is recommended to seek medical attention and treatment as early as possible.