Nipple overflow is one of the common clinical symptoms of breast disease. About 10% of women can be found to have nipple overflow during routine physical examination, and about 35% to 50% of these patients have intra-ductal papilloma and papillomatosis. In the past, the main methods of examination for nipple discharge were cytology, selective mammography and ultrasound, but their diagnostic rates were not high at 50% to 80%, not intuitive and difficult to localize the lesion. A variety of benign and malignant diseases of the breast can manifest as nipple discharge, such as lobular hyperplasia, ductal dilatation, milk retention, intraductal papilloma or intraductal papillomatosis, and breast cancer (early breast cancer including intraductal carcinoma and lobular carcinoma in situ), among which intraductal papillomatosis is also a pre-cancerous lesion of the breast. The clinical diagnosis of nipple overflow is a prerequisite for further treatment. Ductal endoscopy not only greatly improves the diagnostic accuracy of the cause of nipple overflow and enables patients to avoid unnecessary surgery, but also overcomes the shortcomings of mammography and other conventional examination means that are difficult to confirm the diagnosis. The significance of breast ductoscopy is: 1. to clarify the cause of nipple overflow; 2. to refine the indications for surgery and reduce unnecessary surgery; 3. to narrow the scope of surgery and accurately remove the lesion; 4. to allow exploratory treatment of some special types of diseases; 5. to carry out some minimally invasive treatment and minimally invasive surgery with the help of breast ductoscopy.