The diagnosis and differential diagnosis of inflammatory breast diseases is a problem that is easily overlooked in the pathological diagnosis of breast diseases. Accurate pathological diagnosis is of positive significance for timely and correct clinical treatment and alleviation of patient suffering, and the diagnosis of inflammatory breast diseases is increasingly receiving the attention of clinicians and pathologists, whose responsibility is to diagnose granulomatous lobular mastitis, ductal dilatation of the breast, sclerosing lymphocytic lobular It is the responsibility of the pathologist to differentiate diseases such as granulomatous lobular mastitis, ductal dilatation, sclerosing lymphocytic lobulitis and Zuska’s disease, and to make as clear a diagnosis as possible to provide a basis for clinical treatment. The differential diagnosis of inflammatory breast lesions requires attention to the following aspects: ① Pay attention to the clinical features of inflammatory breast lesions, including gender, age, reproductive history, site of occurrence, erythema or pain in the breast, skin breakdown, nipple discharge, nodular erythema in the upper/lower extremities, polyarticular swelling and pain, past history, etc. Clinical manifestations and the clinician’s judgment are essential to suggest the pathologic diagnosis. Different inflammatory breast lesions have different age and gender characteristics: granulomatous lobular mastitis occurs more often in young menstruating women, mostly related to recent pregnancy; ductal dilation of the breast is seen in menopausal and postmenopausal middle-aged and older women; subareolar abscesses often occur in non-lactating women, but can also occur in men and may be related to smoking; sclerosing lymphocytic lobular inflammation is seen in menopausal women, and in men It can also occur in men. The location of inflammatory breast lesions varies: granulomatous lobular mastitis often involves the breast unilaterally, but can also occur bilaterally, mostly in the left breast and mostly in the peripheral part of the breast; ductal dilatation of the breast often involves the breast unilaterally, with lesions often located around the areola; subareolar abscesses can involve the breast unilaterally or bilaterally, with lesions mostly located in the areola area; sclerosing lymphocytic lobulitis involves the breast mostly bilaterally, but can also occur unilateral. The patient’s past history should be taken into account: granulomatous lobular mastitis may be associated with nodular patches in the lower and/or upper extremities and pain in multiple joints such as the knee, ankle, elbow, and wrist, with nodular erythema in the lower extremities with knee and ankle swelling and pain that resolves or disappears with treatment of granulomatous lobular mastitis; subareolar abscesses may be associated with smoking; sclerosing lymphocytic lobular mastitis is often incompletely associated with type 1 diabetes mellitus. diabetes mellitus. ② Pay attention to the imaging manifestations of inflammatory breast lesions: granulomatous lobular mastitis, ductal dilatation, and sclerosing lymphocytic lobulitis manifest as breast masses, which are often misdiagnosed clinically and on imaging as cancer or lymphoma. (3) Gross specimens of inflammatory breast lesions: the boundaries of inflammatory breast lesions are clear or unclear, granulomatous lobular mastitis is solid on the surface, yellow chestnut-like lesions are visible, hard and tough, and needs to be differentiated from cancer; early stage of breast duct dilatation and subareolar abscess are visible on the surface of dilated ducts, and secretions are visible in the ducts, which needs to be differentiated from acantholytic ductal carcinoma in situ; sclerosing lymphocytic lobulitis is solid on the surface, grayish white, hard and tough, and needs to be differentiated from lymphocytic lobulitis in situ. It is hard and tough, and needs to be distinguished from carcinoma. Inflammatory lesions of the breast are by and large tougher and more extensive than carcinoma. Typical microscopic features of inflammatory breast lesions: Various inflammatory breast lesions have typical microscopic features and are not difficult to diagnose, but pathologists need to be aware of the need for a clear diagnosis of these diseases to provide clinicians with an accurate pathological diagnosis to facilitate timely and correct clinical treatment and improve the quality of life of patients. ⑤ Fusion lesions of inflammatory breast lesions: These include multifocal fusion of inflammatory breast lesions and the concomitant presence and fusion of different types of lesions. The main microscopic feature of fused lesions is lamellar chronic purulent (granulomatous) inflammation with visible abscess and granulation tissue formation, atypical lesions, more difficult to distinguish between primary and secondary lesions, and generally occur in pathological specimens from patients with more severe lesions. (6) Concomitant diseases of inflammatory breast lesions: different types of inflammatory breast lesions can be associated with each other, as reported in the literature and observed by the author, granulomatous lobular mastitis and ductal dilatation of the breast can be associated with each other; inflammatory breast diseases can be associated with other types of breast diseases, such as breast fibroadenoma, hemangioma, nipple malformation, etc.; inflammatory breast diseases can also be associated with all other systemic lesions, granulomatous lobular mastitis of the breast Lobular mastitis with lower/upper extremity nodular erythema and polyarticular pain, sclerosing lymphocytic lobular inflammatory disease with type 1 diabetes, and autoimmune diseases such as Hashimoto’s thyroiditis. (7) Relationship between inflammatory breast lesions and cancer: Breast cancer with inflammatory breast lesions is seen in a few literature reports and there is no definite evidence of correlation between the two. The treatment of inflammatory breast lesions varies from one inflammatory breast lesion to another. The treatment of most of the inflammatory breast lesions described above is different from general inflammation, and simple antibiotics are usually ineffective. The main treatment method is surgical excision, supplemented by hormone and important treatment, or simple hormone treatment, which can achieve better results and less recurrence.