Ductal tumor of breast, also known as intraductal papilloma of breast, is a benign lesion, which is not cancerous, but can become cancerous. Clinically, intraductal papillomas are divided into peripheral type and central type, and the central type usually originates from the large duct near the nipple and grows into the ductal lumen in an expansive manner. Sometimes the lumen of the large duct is blocked, but clinically there is no nipple discharge, and sometimes a cystic solid mass is found by ultrasound by chance. If the tumor does not block the ductal lumen, most of them are associated with nipple discharge. The other category is peripheral type, peripheral type is actually the gland outside the nipple areola area, the ductal growth of papillary ductal tumor, called peripheral type, according to the site of origin. Most of the peripheral type of intraductal papillomas are multiple, and these multiple tumors are relatively small and cannot be detected clinically by conventional physical examination and conventional imaging methods. These patients often have nipple discharge, so there is a special test called breast ductoscopy, which can determine the specific location of the tumor and whether it is solitary or multiple.