Granulomatous lobular mastitis (GLM) is an unusual chronic breast inflammatory disease in clinical practice, and its incidence has been on the rise in recent years. However, the misdiagnosis rate of this disease is relatively high due to the unclear pathogenesis and limited knowledge of the clinicians. In addition, the non-standard treatment and unsatisfactory treatment effect will cause repeated bouts of this condition, with delayed and difficult healing. So, it is commonly called “the cancer of inflammation”. Therefore, the Hunan Expert consensus on diagnosis and treatment of granulomatous lobular mastitis (2021 edition) was developed by the organization of five academic institutions that included the Breast and Thyroid Health Management Society of Hunan Provincial Health Management Association, Group of Breast and Thyroid Surgery of Society of General Surgery of Hunan Medical Association, Committee for Prevention and Treatment of Breast Diseases of Hunan Preventive Medicine Association, Society of Surgery of Hunan Association of Chinese Medicine and Integrative Medicine, and Hunan Alliance of Breast and Thyroid Surgery in collaboration with the experts in relevant fields, after detailed discussions of the problems concerning the diagnosis and treatment of GLM both online and offline, striving for perfection and reaching a general agreement.