Nipple discharge is most common in women, during non-pregnancy and non-lactation, when fluid comes out when squeezing the nipple. According to statistics, nipple discharge as the first symptom of medical consultation accounted for 3% to 14% of breast diseases, the incidence of which is second only to breast lumps and breast pain. 1, bloody overflow: red, dark red or coffee color, the most common is caused by intraductal papilloma. There are more breast cancers in bloody overflow, especially intraductal papillary carcinoma, therefore, anyone over 50 years old with single hole bloody overflow should pay special attention to it. Ductal dilatation can also have bloody overflow. 2. Plasma overflow: it is thin, transparent and yellowish, mostly caused by intraductal papilloma, also seen in breast hyperplasia, and a few of them are caused by breast cancer. 3, watery overflow: thin and colorless as clear water, less common, sometimes can also be caused by breast cancer, therefore, should not be ignored. 4, milky overflow: milky white, like milk, can be light or thick. It can be seen in normal women after stopping breastfeeding for several months or years, and it can also be caused by breast hyperplasia or taking some drugs. In addition, it is also common in pituitary tumor. 5, purulent overflow: the performance of viscous yellow or green liquid, can be bloody, like pus. Inflammatory manifestations, mostly seen in mastitis or ductal dilatation.