The lumps that slide on the breasts during breastfeeding may become bigger due to breast hyperplasia, milk stagnation and lymph node enlargement caused by infection. 1. Mammary gland hyperplasia: Postpartum breastfeeding women, due to the need for a large number of milk production, the mammary gland further development, resulting in an increase in mammary gland enlargement, which is a physiological phenomenon, without special treatment. 2. Milk stagnation: breastfeeding women with mammary gland hyperplasia produce more milk, which leads to milk stagnation in the breast. 3. Lymph node enlargement caused by infection: women’s milk stagnation can easily cause breast infection, because milk as a good culture medium for bacteria, bacteria through the milk ducts that the baby bites when sucking, breast infection leads to lymph node enlargement around the breast and can be touched. Breast sliding lumps become bigger during breastfeeding should also be considered benign and malignant tumors of the breast enlarged under hormonal stimulation, and should be consulted in time to clarify the cause of the disease.