Nipple overflow is a common symptom of breast disease and can be divided into physiological overflow and pathological overflow. Physiological overflow refers to the phenomenon of lactation during pregnancy and lactation, bilateral nipple overflow caused by oral contraceptives or sedatives, and unilateral or bilateral small amounts of overflow in postmenopausal women. Clinically, there is still pseudo-overflow – which refers to superficial nipple erosion or leakage from breast fistula, and the corresponding local treatment is feasible. Pathological overflow refers to natural overflow from one or more ducts on one or both sides in non-physiological situations, unrelated to pregnancy or lactation, intermittent and persistent from months to years. Papillary overflow is mainly pathological overflow. The etiology is mostly caused by lesions in the ducts themselves and intra-mammary lesions. For example, intraductal papilloma, cystic hyperplasia, ductal dilatation, ductitis, intraductal carcinoma, etc., which account for more than 80% of all nipple overflow. Nipple overflow is often unilateral and can occur on both sides at the same time. The overflowing ducts can be single duct or multiple ducts. Unilateral single duct nipple overflow is commonly associated with intraductal papilloma; unilateral multiductal overflow is commonly associated with ductal dilatation of the breast and cystic hyperplasia of the breast; bilateral multiductal overflow is commonly associated with endocrine disorders, drug reactions, amenorrhea-overflow syndrome or certain benign breast diseases. Pathological overflow is determined by the nature of the overflow, cytological examination (overflow cytology, lump needle aspiration cytology), and what is seen on mammography to determine whether the overflow is due to a tumor. Biopsy is the most reliable method to confirm the etiology of nipple overflow, especially for early microscopic tumor foci, when imaging and cytology diagnosis is negative and clinical suspicion is performed. Treatment of non-neoplastic overflow: often caused by ductal dilatation of the breast and cystic hyperplasia of the breast. The former can be treated medically or surgically, while the latter can be treated with herbal medicine, medication or surgery. Treatment of tumor overflow: It is often caused by intraductal papilloma or intraductal papillary carcinoma. In the former case, local segmental excision should be performed, and in the latter case, radical mastectomy for breast cancer should be performed.