Plasmacytoid mastitis, also known as ductal dilatation, is a chronic non-bacterial inflammatory disease of the breast. Treatment requires attention to the following aspects: First, if the patient has significant local inflammation, he or she should be treated with a combination of antibiotics including anti-anaerobic bacteria, or a combination of Chinese and Western treatments. Second, if the patient’s abscess forms later, it often breaks down on its own to form a fistula, and there is a breast lump or the nipple appears to be overflowing with a thick mucous discharge, the patient should undergo surgery at this time. The following two types of surgery are commonly used: 1. excision of local masses, which is suitable for patients with simple breast masses and limited masses; 2. excision of quadrant, hemithorax and mammary gland, which is suitable for patients with large masses and lesions occupying the whole breast or most of the breast.