Breast swelling and pain is a common symptom, the causes of breast swelling and pain may be: 1, before or during menstruation, breast swelling and pain may occur, due to changes in estrogen levels in the body, it is a normal physiological phenomenon. 2, in the case of breast swelling and pain during the period of non-menstruation, may be due to breast hyperplasia, breast fibroids, and other diseases, the symptom will be more pronounced in the menstrual cycle, can be ultrasound examination to clarify the cause before treatment. 3, women in pregnancy due to changes in hormone levels, is a normal physiological response. If you have a breast cancer, you can have an ultrasound examination to clarify the cause of the disease before treatment. 3, during pregnancy, due to changes in hormone levels in the body, there will also be breast swelling and pain, which is a normal physiological reaction and does not require treatment. 4, lactating women due to the accumulation of breast milk, there may be a situation of milk distention, which will also cause breast swelling and pain, you need to empty the breast milk in a timely manner, in order to avoid triggering acute mastitis and so on.