In clinical practice, mastoplasmacytic mastitis is a very difficult problem, often a long and painful treatment process for doctors and patients. In the clinic, we have encountered patients who have suffered severe disfigurement of the breast due to multiple surgical incisions and repeated ruptures, patients who are emaciated due to repeated incomplete surgical treatment, and patients who are determined to have their entire breast removed (simple mastectomy) because the lesion does not heal over time. Mastoplasmacytic mastitis is characterized by marked dilatation of the collecting ducts at the areola, periductal fibrosis and numerous inflammatory cells, especially plasma cell infiltration. In the past, the nomenclature was confusing. It is also known as non-lactating mastitis because it often occurs during the non-lactating period. In particular, it is thought that the cause of the lesion is dilation of the milk ducts, so it is called ductal dilation of the breast. Currently, the term plasmacytic mastitis is largely unified. The etiology of this disease is not yet universally understood. The disease is more common in women aged 30 to 40 years who have given birth, are not breastfeeding, and in older postmenopausal women. The clinical features of plasmacytoid mastitis are: ① occurring during the non-lactating period ② associated with nipple hypoplasia or nipple deformity (nipple depression, split nipple, flattened nipple, etc.) ③ recurrent episodes of fistulas that do not heal ④ the appearance of the breast is easily disfigured and easily misdiagnosed and treated clinically. The clinical manifestations of mastoplasmacytic mastitis are atypical and diverse, and may not have any clinical symptoms. In the presence of ductal fibrosis and chronic inflammatory cell infiltration, one or several hard, round masses of varying size may be found in the breast. The masses are most often located in the central region of the breast. The masses are usually flat and nodular, with the nodes being hard and the interstitial part of the nodes being soft. Most of the masses are associated with chronic inflammatory changes. Some cases sometimes show acute inflammatory changes, with swollen, painful, red breasts and abscess formation, generally with a long duration of disease, inflammation can be recurrent, antibiotic treatment is usually ineffective. ② nipple overflow: nipple overflow is mostly watery, serous, brown or milk fat-like fluid, or thick pus-like secretions, bloody fluid is rare. ③Increased nipple: In a few cases, the nipple and its surrounding skin are sunken or the nipple is deviated due to contraction of the fibrous tissue of the duct wall, which mostly occurs in those with subareolar masses. This is often misdiagnosed as breast cancer. ④ Non-cyclic breast pain. Clinically, mastoplasmacytic mastitis is often divided into two types: i. Fistula type: i.e. chronic recurrent parareolar abscesses or fistulas. It is most often seen in unmarried girls or young women, and 90% are associated with nipple developmental malformations. Because the nipple is dysplastic, nipple inversion inevitably causes distortion and deformation of the duct and poor discharge of the contents. The inversion of the nipple (indentation) causes the natural shedding of epidermal cells to accumulate, moisten and erode, triggering the blockage of the outlet of the milk duct, and the accumulation and degeneration of fatty substances in the large duct, stimulating the duct wall and triggering the inflammatory reaction around the duct. Because lipid-like substances are produced autologously, the induced inflammation is a metaplastic reaction. It is not a purulent inflammation caused by bacterial infection as in acute mastitis during lactation. Therefore, the inflammatory reaction is slow, with mild initial symptoms, no fever, and no severe pain. It is not until a part of the areola next to the breast becomes red, swollen or a small abscess that you seek medical attention. If the receiving physician does not recognize the disease and thinks that it will be fine if it is cut and drained like a small abscess on other parts of the body. The fistula is actually formed long ago, and the inner mouth of the fistula is in the infundibulum or the large duct near the nipple, where the columnar epithelial cells of the large duct transform into squamous epithelium and form an inflammatory necrotic lesion. If the lesion at the inner port and the entire fistula are not removed, the outer port will not heal, and incision and drainage can only solve the abscess problem and cannot completely cure the disease. Second, the mass type: that is, a chronic inflammatory mass that can have multiple breakdowns. It is mostly seen in middle-aged women and is mostly associated with nipple entropion or splitting, but there are also those with normal nipples. The onset may be associated with ductal dilatation. The mass is distant from the nipple and adheres to the skin, much like breast cancer. The masses show chronic inflammatory changes, are tough, poorly defined, slightly painful, and can increase in size suddenly, or sometimes large, sometimes small. The erythema ruptures and forms multiple complex fistulas or sinus tracts, and the rupture is always connected to the lesion behind the nipple, so local incision to clear the sore is not likely to heal. The biggest problem in the diagnosis of this lumpy form of mammary plasmacytosis is how to differentiate it from breast cancer, and there have been reports of mistaken radical breast cancer surgery. Aspiration cytology can be performed if necessary. If the diagnosis of plasmacytoid mastitis is confirmed, the inflammatory mass is large and treated with herbal medicine to make the mass smaller. It is usually necessary to take medication for more than one month for the best timing of surgery, complete removal of the lesion, maximum preservation of normal breast tissue, maintenance of breast shape, and nipple inversion plastic surgery. Plasmacytoid mastitis is very easy to misdiagnose before surgery, especially if there are no skin changes. The most important clinical significance of this disease, which is not precancerous, is to differentiate it from breast cancer. If the initial lesion is distant from the nipple or located deep in, this chronic inflammatory mass, which can cause skin adhesions, is not easily distinguished from breast cancer. If it is a multiple fistula with constant pus, it can be misdiagnosed as breast tuberculosis. Surgical excision of the lump for biopsy is the fundamental measure to confirm the diagnosis and treatment. Chinese medicine treatment is effective in the treatment of plasmacytoid mastitis. Surgical treatment mainly focuses on the dilated ducts and the degree of inflammation around the ducts to choose different treatment methods. The timing of surgery is well controlled, and the timing of surgery is facilitated by a combination of Chinese and Western medicine treatment. Complete excision of the lesion is advisable by making an incision next to the areola, turning the areola, removing the lesion around the large diseased duct, and removing all the inflammatory necrotic part up to the normal gland, but in principle, simple mastectomy should be avoided.