Hard lumps appear in the breast during breastfeeding, without pain, consider the following reasons: 1. Milk stagnation during breastfeeding. With too much milk and poor drainage, milk can pool into lumps. Milk stagnation is the prelude and basis of bacterial infection. The lactation is mostly caused by inexperience or improper methods of breastfeeding, and pathogenic bacteria invade the breast parenchyma through the nipple skin break or the milk duct, forming mastitis. This is a good way to prevent mastitis. 2. breast tumors. This can be seen in breast cancer, breast fibroadenoma, breast lobular tumor, etc. The nature of the tumor varies, and the lumps are different. The shape, size, hardness and mobility of the lump can be different depending on the nature of the tumor. You can go to the hospital for ultrasound examination of breast surgery, or have a puncture biopsy of the lump for pathological examination to clarify the nature of the lump. Women can also have breast enlargement during breastfeeding. The main symptom of breast enlargement during lactation is periodic pain in the breast, which occurs in women between the ages of 25 and 45, and the pain increases before menstruation and may subside or disappear after menstruation. In severe cases of breast enlargement during lactation, the pain can be persistent before and after menstruation. The main reason for the occurrence of breastfeeding mastocytosis is that the endocrine hormones in women’s bodies become dysregulated after childbirth, and the normal growth of the breast is affected, and then there is the influence of mental factors. For treatment, it is necessary to make yourself spiritually optimistic attitude, pay attention to the hygiene of the breast, try to let the child drink all the breast milk in the breast at once when breastfeeding, and keep the nipple clean. The duration of breastfeeding can be extended appropriately. If you have lumps in the breast other than breastfeeding hyperplasia, you need to go to the hospital for ultrasound or aspiration pathology to clarify the condition.