Definition Non-lactating breast inflammation is a group of non-specific inflammatory conditions that occur in women during the non-lactating period. Clinically, it is characterized by breast lumps, nipple inversion, nipple overflow and breast abscess, and even the formation of periampullary fistula or sinus tract. They mainly include mammary duct dilatation/periductal mastitis (MDE/PDM) and granulomatous lobular mastitis (GLM). Its onset can affect adult women of all ages. Etiology Obstruction Theory Inverted nipple and blocked milk ducts lead to blockage of secretions, which causes aseptic inflammation followed by bacterial infection leading to the development of the disease. Infection theory A variety of bacterial infections such as enterococci, anaerobic streptococci, Brucella, and Mycobacterium have been reported to cause this disease. Recent studies have shown a strong association between granulomatous mastitis and Mycobacterium bovis infection. Smoking Overseas literature shows that heavy smoking is closely related to the occurrence, development and recurrence of MDE/PDM, but the mechanism is not clear. Other factors Some scholars have suggested that GLM is related to autoimmune factors, contraceptive use, hyperprolactinemia, and inflammatory reactions caused by trauma. Clinical staging Invisible type The main manifestation is breast swelling and pain or nipple overflow. The pain is not related to the menstrual cycle. Nipple discharge is often intermittent, mostly unilateral, can occur in multiple ducts, the discharge can be serous, white or cheese-like. Lump type The main manifestation of the first diagnosis of this type of disease, the lump is located around the areola, flat or nodular, may be accompanied by nipple inversion. Abscess type In chronic lesions on the basis of secondary acute infection abscess formation, severe cases may be accompanied by local redness, swelling, burning, tenderness, but systemic symptoms are rare. Fistula Rarely, fistula or sinus tract is formed after abscess self-rupture or drainage.