Mammary ducts, also known as milk ducts, are made up of interlobular milk ducts that converge from small milk ducts and are mainly located in the subcutaneous tissue of the chest, which is one of the most important parts of the breast, and together with the glands, fibrous tissue, and adipose tissue, they form the entire breast. There are about 15-20 milk ducts in a woman’s unilateral breast, which radiate to the whole breast with the nipple as the center point. Each milk duct connects to a breast lobe at one end and goes to the nipple at the other end, which is an important pipeline for storing and discharging milk. Common diseases of the milk ducts mainly include dilatation of the milk ducts, cancer of the milk ducts, etc. Symptoms are mainly intermittent nipple overflow, lumps, pain, and changes in the skin tissue of the nipple, etc., which require special attention to care and observation, and once such symptoms occur, you should go to the hospital for medical treatment in a timely manner.