Ductal dilatation of the breast is a comprehensive syndrome characterized by dilatation of the breast ducts, accumulation of secretions, overflow, ductitis, chronic recurrent inflammatory masses in the breast, fistula, and nipple invagination, which occurs under the action of pathological factors such as poor drainage of the breast ducts, blockage, endocrine disorders, and infection. A common symptom of ductal dilatation is nipple discharge. The nature of the discharge can be watery, or plagioid, or cheesy. The discharge is spontaneous, often occurs intermittently, and can last for a considerable period of time. The amount of overflow can be large or small. Cytologic examination of the overflow often reveals disorganized cellular debris, foam cells, lipophilic cells, histiocytes, giant cells, neutrophils, and glandular epithelial cells. As the disease progresses, the walls of the dilated milk ducts become thickened due to fibrosis along with inflammatory response and lymphoproliferation, making the milk ducts shorter and causing nipple retraction. The earliest nipple change is a central depression with a horizontal labral change of the nipple, which can gradually progress to an incomplete depression and complete depression. There are also cases of poor ductal drainage due to pre-existing congenital nipple indentation, which eventually leads to dilation of the milk ducts. If edema is present in the areola, pseudocellulite may be seen. When the ductal expansion develops further, or under the stimulation of the decomposition products of the ductal contents, or after trauma (including surgery and impact), the epithelium of the continuously atrophied milk duct ruptures continuously, and the intracanalicular secretions pass through the ductal wall, causing inflammation of the tissue around the duct, resulting in the formation of a mass under the areola or around the areola, and when the inflammation spreads to the surrounding area, the mass expands rapidly, and this process is rapid, often within 2-3 days. The lump occupies most of the breast within 2-3 days, and is often misdiagnosed as breast cancer due to its rapid enlargement, stiffness, indistinct margins and adhesions to surrounding tissues, orange peel-like changes in the local skin, nipple retraction and enlarged axillary lymph nodes. A large number of lymphocytes and plasma cells can be seen on cytological examination or pathological section, thus it is also called plasma cell mastitis. Sometimes granulomatous tissue and Wolfram’s giant cells can also be seen. When an abscess is formed, there may be less obvious localized skin redness, fever, swelling and pain in the breast, and systemic symptoms such as low-grade fever, fatigue, dizziness or headache, etc. After the abscess breaks down, a fistula may form, or the abscess may be cured temporarily, but later recur, and often after the onset of one side, the same lesion may appear on the other side. Some people call this stage of the disease “areolar duct fistula”. Surgery is an effective treatment for this disease. Different surgical methods are used depending on the stage of development. The method is to make a curved incision along the edge of the areola, preserve the nipple, remove all dilated ducts from below the nipple, and wedge the breast mass under the areola. 2. Segmental mastectomy: This is indicated for subareolar masses with peri-mammary ductitis. The large ducts and the tissue surrounding the mass should be removed from the nipple to prevent the formation of subareolar cysts, mammary fistulae and nipple overflow after surgery. 3.Simple mastectomy: It is suitable for those with extensive lesions and large masses, especially those located under the areola with skin adhesions forming sinus tracts. Total percutaneous mastectomy or simple mastectomy can be performed.