Granulomatous mastitis is a group of chronic inflammatory diseases of the breast with granulomas as the main pathological feature and of unknown etiology. Granulomatous inflammation is centered on the lobules of the breast, hence the name granulomatous lobular mastitis (GLM), which was first reported by Kessler in 1972 and the name is recognized by most scholars. It was previously called idiopathic granulomatous mastitis, mammary granulomatosis or granulomatous lobulitis, a granulomatous lesion of the breast with non-caseous necrosis confined to the lobules, in which no pathogen can be identified and which may be an autoimmune disease, like granulomatous thyroiditis and granulomatous orchitis, easily confused with tuberculous mastitis, the incidence of which used to be low, so it was not much observed and studied by clinical and pathologists. In recent years, the incidence has gradually increased. The etiology and pathogenesis of granulomatous lobular mastitis is unclear and may be related to the following factors: ① autoimmunity, most researchers believe that granulomatous lobular mastitis is an autoimmune disease, but there is no clear evidence; ② oral contraceptives; ③ taking antipsychotic drugs, some studies have shown that antipsychotic drugs cause increased prolactin secretion by blocking dopamine (DA) receptors, resulting in hyperprolactinemia (4) hyperprolactinemia; (5) hypersensitivity reaction induced by milk stimulation; (6) pituitary adenoma; (7) trauma; (8) elevated blood IgG4, with two cases reported in the literature as coexisting with IgG4-associated mastitis; (9) possible potential source of infection. Clinical manifestations Most often occur in women of childbearing age with a history of childbirth, occasionally reported in the literature in women who are lactating, pregnant or without a history of childbirth, no male cases have been reported. The age of onset is 19 to 46 years old, with a median age of 32 years, and the majority have a history of childbirth, with the youngest child being 1 month to 8 years old and the median being about 3 years old. Combining our case collection with the national and international literature, the majority of patients with granulomatous lobular mastitis without a history of childbirth had a history of antipsychotic medication. The clinical presentation is a breast mass, often with unilateral breast involvement, but can also occur bilaterally, more commonly in the left breast, mostly in the peripheral part of the breast. It may be associated with pain, skin erythema, rupture, sinus tract formation, nipple discharge, nipple deformation, invagination, and in a few patients, axillary lymph node enlargement. Nodular erythema of the lower and/or upper extremities and multiple joint swelling and pain of the knee, ankle, elbow and wrist may occur, with nodular erythema of the lower extremities with knee and ankle joint swelling and pain being the most common. III. Treatment and prognosis Granulomatous lobular mastitis is a non-bacterial inflammation of the breast, and incision and drainage can easily lead to difficult healing of the incision and formation of sinus tracts. There are different views on the preferred treatment modalities reported in the domestic and international literature, and the available treatment modalities are surgical excision, hormonal, herbal or palliative treatment, and ineffective antibiotic treatment. Some scholars believe that granulomatous lobular mastitis with nodular erythema should be treated mainly with hormonal therapy, and patients with hyperprolactinemia caused by antipsychotic drugs should be treated conservatively. If the treatment is inappropriate or untimely, it is easy to relapse and persist.