Granulomatous mastitis has a poorly defined appearance and is characterized by a painful localized breast lump that is hard and irregular in shape. If the onset is sudden or the lump increases in size, there is redness of the skin and the formation of a small abscess, which breaks down with little pus and does not heal, with redness, swelling, and breakage occurring one after another. Granulomatous mastitis is a granulomatous inflammation of the lobules of the mammary glands caused by autoimmune diseases, trauma, or localized infections that cause the ductal epithelium to break down and the contents of the ductal lumen to enter the interstitium of the lobules. When similar symptoms occur, it is necessary to go to the hospital in time to confirm the diagnosis through physical examination, magnetic resonance imaging and blood tests.