Limited dilatation of breast ducts refers to the local dilatation of breast ducts due to relative narrowing of the proximal section of the ducts by inflammation, tumor compression, etc. or abnormal secretion of sex hormones. It is caused by blockage or narrowing of the proximal nipple side of the breast ducts due to inflammation, tumors, or traumatic injuries, resulting in retention of secretion in the ducts, which causes the dilatation of the breast ducts. If there is mastitis, anti-infection treatment can be given; if there is a tumor, such as intraductal papilloma, breast cancer, breast cysts, etc., surgical treatment is needed; trauma-induced dilation of the mammary ducts is usually not harmful to health and can be left untreated. Polycystic ovaries, hyperprolactinemia and other sex hormone-secreting tumors can cause an increase in the secretion of sex hormones in the body, which on the one hand promotes the expansion of the milk ducts, and on the other hand prompts an increase in the secretion of the milk duct epithelium, which makes the expansion of the milk ducts obvious in both aspects. These pathologic conditions require identification of the specific cause and appropriate symptomatic treatment.