To prevent breast cancer you must be alert to the occurrence of the following problems 1. Lumps: The majority of patients visit the clinic with a lump found inside the breast. It is generally considered to be irregular in shape, with unclear edges and hard texture. There is also a rare type of breast cancer called occult breast cancer, in which the lump in the breast cannot be detected, but the axillary metastasis has already appeared. Pain: Most of the patients have no obvious pain, but a few of them visit the doctor with pain, which is mostly paroxysmal stabbing pain or hidden pain. Non-to advanced pain is not serious. 3. Nipple overflow: bloody nipple overflow. 4. Skin changes of breast: Skin changes of breast cancer are related to the depth of the lump and the degree of invasion. The skin may show dimples and orange peel-like changes. 5. Nipple changes: Nipple invagination is an important sign of cancer in the central area of the breast, and it is difficult to pull out the nipple with fingers. In the case of eczema-like carcinoma, the nipple is vesiculated and often has scabs. 6.Change of breast shape: normal breast shape is naturally curved, if the curvature is abnormal, attention should be paid to the occurrence of cancerous tumor.