After stopping breastfeeding, hard lumps are found in the breasts, mainly due to the following reasons: firstly, consider whether it is milk lumps, which is mainly due to the milk stagnation in the milk ducts, and the absorption of milk after a long period of no breastfeeding to form milk lumps. Secondly, breast fibroadenoma, because breastfeeding causes changes in the level of estrogen in the body, estrogen is a stimulating factor for breast fibroadenoma, some patients before and after pregnancy breast fibroadenoma will suddenly increase in size, and after stopping breastfeeding the breasts return to their normal shape, the fibroadenomas are more obvious. Finally, breast cancer can also occur during pregnancy and breastfeeding, and the clinical manifestations are the same as ordinary breast cancer. Clinical diagnosis is usually late, and it is recommended to perform breast ultrasound, molybdenum target, MRI or breast lump aspiration biopsy to clarify the nature of the lump, and if it is breast cancer, it needs to undergo surgery as early as possible.