The incidence of pathologic nipple discharge in women with breast disease is about 3-8%, of which the incidence of breast cancer is 4-31%, and the incidence reported in most of the literature is 10-15%. Pathological nipple discharge, especially bloody nipple discharge, is one of the signs of early breast cancer, so the diagnosis of breast disease associated with pathological nipple discharge should be taken seriously by clinicians. Pathological nipple discharge breast diseases include intraductal papilloma (40-70%), cystic hyperplasia of the breast (25%), ductal dilatation (10%-15%), mastitis, breast fibroadenoma and breast cancer (10-15%). Specific diseases include: 1. Ductal dilatation of the breast Ductal dilatation of the breast accounts for 4.5% of benign breast diseases, due to lactation disorders, anaerobic bacteria, endocrine dysfunction and degenerative changes in the breast, causing the shedding of mammary epithelium and blockage of ducts by the accumulation of large amounts of lipid-containing secretions, resulting in poor excretion of secretions, increasing pressure in the ducts and causing ductal dilatation, with varying degrees of inflammation and fibrosis around the ducts. There are varying degrees of inflammation and fibrosis around the duct. There are three clinical phases: acute, subacute, and chronic, with overflow, mass, and mixed types, and the lesions are located below the nipple. The clinical features are: (1) it occurs in non-lactating or menopausal women between 40 and 60 years of age, with a history of lactation disorders; (2) nipple overflow is the first symptom in the early stage, often bilateral overflow from multiple ducts, with a large amount of purulent, bloody or dark green thick fluid; (3) nipple overflow and swelling can be seen on needle aspiration cytology with a large number of ductal epithelium, foam cells, plasma cells, lymphocytes, cell remnants and necrotic material. 2, breast hyperplasia In cases of milk-like, watery, and some cases of plasma overflow, a high proportion is due to breast adenopathy or cystic hyperplasia. 3.Central type intraductal papilloma Central type papilloma occurs in large ducts or dominant ducts and is most common in women aged 40 to 50. Nipple overflow is the most common symptom and only a few breast lumps can be palpated. Peripheral papilloma is equivalent to the former intraductal papillomatosis, which originates from TDLU, is often multicentric and can extend into the adjacent large ducts, and the age of onset is similar to or slightly younger than the central type. Most clinical examinations resemble fibrocystic breast disease, with few palpable masses and uncommon nipple discharge. Intraductal papilloma accounts for 20% of benign breast tumors and is second only to mammary fibroadenoma in incidence, and has a certain rate of malignancy (6%-8%). 5.Intraductal carcinoma The incidence of intraductal carcinoma accounts for 15%-30% of breast malignant tumors. The clinical manifestations of intraductal carcinoma are calcified foci (76%), inaccessible lumps (11%), or lumps combined with calcification (13%), and small amount of nipple discharge, especially bloody nipple discharge, shown only on mammogram. Invasive ductal carcinoma rarely has nipple discharge as the first symptom and can be diagnosed without endoscopic examination.