Plasmacytoid mastitis, also known as ductal dilatation, is not caused by bacterial infection, usually without fever, and can subside and absorb on its own, but it is prone to recurrent episodes, and even breaks down to form fistulas, with different clinical manifestations at different times of the disease. The exact cause of plasma cell mastitis is not clear, but it is believed that the occurrence and development of the disease may be caused by the following factors: ① Blockage of large milk ducts leading to poor drainage of the milk ducts. The main causes of milk duct obstruction are nipple dysplasia (e.g., nipple entropion, nipple lobing, flat nipples), milk retention or difficulty in breastfeeding during lactation, inflammation, trauma, and surgery in the areola area involving the milk ducts, and possibly autoimmune and endocrine dysfunction. (ii) Inflammation around the milk ducts: distortion, deformation and obstruction of the ducts under the areola, causing dilation of the ducts, accumulation and overflow of fatty material in the ducts, and breakage of the milk duct walls, causing chemical irritation and immune reaction around the ducts, resulting in a large number of plasma cell infiltration. (③) Bacterial retrograde infection: poorly ventilated milk ducts can be secondary to bacterial infection, and the course of the disease transforms from aseptic inflammation to purulent inflammation. The initial lesion may be only localized redness and swelling, and then an abscess may be formed, and a sinus tract may be formed after chronic recurrent attacks. Clinical features 1, more young women, unmarried can also occur. Most of them are not related to pregnancy and lactation, i.e. they do not develop during lactation. 2. Unilateral onset is more common, but there are also cases where both breasts develop one after another. The course of the disease is slow and can last for months or years. 3. Most patients have various deformities of the nipple or dilated ducts. The initial stage is localized redness, swelling and pain next to the areola, and when suppuration occurs, the mass may be locally red and swollen but the systemic inflammatory reaction is not typical; repeated attacks, which do not heal for a long time, may form a fistula next to the areola or a chronic inflammatory mass, and after the abscess breaks down, the pus is often mixed with grease-like material, and repeated attacks and fistulas leading to the nipple are formed; 5. deformation. 6, easy to misdiagnose and mismanage. Some clinicians do not know enough about it and easily mistake it for septic mastitis or misdiagnose it as breast tuberculosis, thus delaying treatment. If the lesion is far from the nipple, or located deep in, this chronic inflammatory mass, which can cause skin adhesions, is not easily distinguished from malignant tumors of the breast. Clinical manifestations 1. Overflow phase: Nipple overflow is an early manifestation of plasmacytoid mastitis and is often overlooked. The overflow is mostly intermittent, spontaneous, and can last for a long time. Some patients have complete or incomplete nipple indentation, which is congenital in a significant proportion of patients, and in some patients nipple indentation occurs gradually after the onset of the disease. 2.Lumpy stage: It often starts suddenly and develops rapidly. Patients feel localized pain and discomfort in the breast, which can be tingling or vague, and a lump is found. The lumps are mostly located under the areola or extend in a certain direction. The masses are of different sizes and irregular shapes, with a hard and tough texture and a nodular surface with poorly defined borders. In the acute stage, the lump may be locally red and swollen, with significant pain and even edema of the breast skin, similar to acute suppurative mastitis, but usually without chills and fever and elevated blood count. A small number of patients can also always be dominated by breast lumps, which gradually increase in size and last for several years, but always without obvious redness or swelling. 3, fistula stage: later breast lumps appear softening, forming abscesses, breaking down and flowing pus, in which grease-like material is visible. The wound is repeatedly ulcerated and the local tissue is hard and uneven. Fistulae are often formed, both simple and complex, with the inner mouth connected to the opening of the milk duct at the nipple and the outer skin mouth mostly located in the areola. The first is a conservative treatment that includes physiotherapy, external application of traditional Chinese medicine and oral administration of traditional Chinese medicine. 2. For patients with obvious redness, swelling and pain in the acute stage, intravenous antibiotics are given; if an abscess is formed, the abscess is incised and drained, and local medication is changed; 3. After the acute inflammation subsides, if there is a local mass, the lesion is surgically removed, and the scope of removal should include a small amount of normal tissue. 4. For those who have formed chronic fistulae, because the internal opening of the fistula is in the infundibulum or large duct under the nipple, which is the core of the lesion, the fistula needs to be removed up to the underside of the nipple and the complete removal of the lesion and the affected duct is necessary to avoid recurrence. Plasmacytoid mastitis requires complete surgery, otherwise it will recur after surgery and is a difficult disease to treat. We have successfully treated many patients with plasmacytoid mastitis with individualized treatment plans, and have minimized the damage to the breast while ensuring the effectiveness of the treatment. For some patients with large lesions, we also combine plastic surgery to achieve an aesthetically pleasing postoperative appearance. Very good results have been achieved.