Hard lumps in breasts during breastfeeding may be caused by breast milk stagnation, breast fibroadenoma, chronic lymphadenitis, breast cancer and other diseases. 1. Milk stagnation, breastfeeding obstacles caused by nipple dysplasia, excessive milk, so that the milk can not be completely emptied, will lead to milk stagnation in the milk ducts to form a hard knot. This can be relieved by localized hot compresses on the breasts, breast massage, and sucking the milk out with a breast pump, etc. The prolonged stagnation of milk may be followed by infection and cause mastitis. 2. Breast fibroma, which usually causes painless lumps in the breasts, can be treated with regular follow-up or surgery depending on the condition. 3. Chronic lymphadenitis, which is a prolonged irritation caused by chronic inflammation, resulting in enlarged lymph nodes, manifested as hard lumps in the breast with mild pain or no pain. 4. Breast cancer, early painless lumps can appear, should be carried out timely molybdenum target examination and pathology biopsy, diagnosed according to the condition of surgery, radiotherapy and other comprehensive treatment. It should be noted that when painless hard lumps appear in the breast, you should go to the hospital in time for examination and treatment under the doctor’s guidance.