A lump next to the nipple during breastfeeding may be related to milk stagnation, mastitis, breast hyperplasia, breast cancer and other conditions. 1. Milk stagnation: During the breastfeeding period, as milk is always secreted, if there is milk left inside the breast after breastfeeding, and the milk is not squeezed out in time, it may be stagnated and blocked, resulting in localized lumps. 2. Mastitis: If the breast milk is more serious and the lump is hard like a stone, accompanied by redness, swelling and hot pain on the surface, it may be mastitis. 3. Mastoid hyperplasia: Patients with mastoid hyperplasia will have hard nodules inside their breasts, which may be accompanied by nipple discharge and other phenomena. Symptoms are more obvious especially when you are angry or before menstruation. 4. Breast cancer: On this basis, if accompanied by nipple blood, breast orange peel-like changes and other symptoms, need to be alert to breast cancer. It is recommended that the patient should consult a doctor in time and do systematic examination in strict compliance with the doctor’s instructions to clarify the cause of the disease.