The causes of sudden nipple inversion mainly include the following aspects:1. Due to the patient’s local anatomical relationship, there is a slight inversion of the nipple itself, with the passage of time, the patient’s mammary gland status changes, and the inversion of the nipple will be aggravated.2. Reaction caused by inflammation of the mammary glands, when mastitis occurs, it will invade the ligament inside the mammary glands, the inflammation reaction will aggravate and the ligament will shorten, and the nipple will be pulled in, with plasma cell mastitis being the main cause. 3. 3, the clinical manifestation of breast cancer, breast cancer cancer cells invade the ligament of the breast gland, which will also cause the ligament to shorten, causing nipple inversion, in order to further clarify the diagnosis, the patient can go to the hospital to do ultrasonography, basically to determine whether there is any obvious space-occupying lesions in the breast, if there is not can explain the cause of nipple inversion, but also make an important basis for the next step of the treatment. If it exists, it can explain the cause of nipple inversion and provide an important basis for the next treatment.