The appearance of a red lump under the breast may be due to several clinical causes: one is a skin boil under the breast, which is usually red and swollen or accompanied by significant pain and fever in severe cases. Another condition is the possibility of some hemangioma. Although this condition is relatively rare, very few patients in the clinic can indeed find a red lump on the skin surface of the breast, and when pressed, the color recedes, and when the pressure is reduced or released, the lump or lump recovers and becomes red again, which is more typical of hemangioma on the skin surface. Therefore, if there is a red lump under the breast, you must go to a hospital breast specialist for a detailed examination to find the exact cause of the disease before specific treatment can be given.