The presence of blood overflow in the breast may or may not be serious, depending on the specific condition, and the less serious cases include intraductal papillomas and cystic hyperplasia of the breast. The serious ones are breast cancer. 1. Non-serious cases: benign breast diseases such as intramammary papilloma and cystic hyperplasia of the breast will appear bloody overflow, at this time, patients do not need to worry about it, and it is usually not serious. Intramammary papilloma occurs in the milk ducts near the nipple, and its tumor is small, which may invade the thin-walled blood vessels, and then cause bloody overflow. Cystic hyperplasia of the breast can be found on both sides of the breast in nodules of varying sizes that are hard and poorly demarcated from the surrounding tissues, and patients may present with bloody discharge from one or more of the milk ducts. Intramammary duct papilloma and cystic hyperplasia of the breast are benign lesions of the breast, which need to be reviewed regularly. 2. Serious cases: patients with breast cancer may also have bloody breast overflow, especially in the case of intraductal papillary carcinoma, where the cancer invades the blood vessels in the breast and causes the blood to flow out. It suggests that the patient’s condition is serious and needs timely treatment. Meanwhile, mastitis and ductal dilatation can also cause bloody discharge and should be distinguished. There are many causes of bloody breast discharge, and it is recommended that patients with bloody breast discharge need to consult a doctor in time to find out the cause of the disease, and do not use medication on their own to avoid danger.