The cause of chronic pyogenic granulomatous mastitis is not yet clear, but may be related to the stimulation of milk secretion, trauma infection, autoimmunity and other factors. 1. Milk secretion stimulation: chronic suppurative granulomatous mastitis can’t be ruled out due to secretion or milk stagnation retrograde to the interlobular matrix of the mammary gland, so it will further cause inflammation. 2. Trauma infection: when the patient has a trauma or impact on the breast area, it may increase the chance of infection of the interlobular matrix of the mammary gland, and then form granulation tissue, which will lead to chronic suppurative granulomatous mastitis disease. 3. Autoimmunity: Some patients may have low immunity, and when they suffer from external chemical stimuli or infections, it is easy to injure the breast ducts, which in turn leads to chronic pyogenic granulomatous mastitis. There may be other causes of chronic pyogenic granulomatous mastitis, so it is recommended that the patient should go to the hospital, cooperate with the doctor to complete the relevant examinations and determine the cause of the problem before treatment and therapy.