There are many reasons for a sudden lump in the breast, as follows: 1, breast lymph nodes, lymph nodes will increase in size and pain when stimulated, but they can move and are relatively smooth. You can infuse anti-inflammatory or surgical removal, but do not massage, stimulate. 2, breast hyperplasia, breast hyperplasia patients in the breast hard lumps with clear edges, no adhesions with the surrounding tissue. The hard lump is related to the physiological period, the hard lump starts to be painful at the beginning of the menstruation, and the pain disappears at the end of the menstruation, you can take breast fetish elimination or prolotherapy pills. 3, milk stagnation, breast duct deformity or nipple deformity causes milk to gather inside the breast, forming a hard lump, you can find a professional to massage and unblock or use a breast pump. 4, breast fibroids, generally no symptoms, during lactation and pregnancy will suddenly increase, need Early surgical removal is needed to prevent malignant changes.