Breast pain before menstruation may be a normal physiological phenomenon, or it may be related to breast hyperplasia and breast tumor. 1. Normal physiological phenomenon: Before menstruation, the hormone level in women’s body will change, and the estrogen and progesterone in the body will be elevated, which may lead to breast swelling and pain, and there may also be symptoms such as impatience, irritability, abdominal distension and pain, etc. These symptoms will be gradually relieved and disappeared after the onset of menstruation. 2. Mammary hyperplasia: Mammary hyperplasia is the most common benign breast disease in clinic, which may cause breast pain, nodules or lumps, and some patients may combine with nipple discharge. Some patients may have nipple discharge. Patients with breast enlargement may experience breast swelling and pain before menstruation. 3. Breast tumor: Breast tumor is a benign or malignant tumor that occurs in the breast, often manifested as a lump in the breast, and may feel breast swelling and pain when hormone changes occur in the body before menstruation. There are many causes of breast swelling and pain, we should consult a doctor in time to clarify the cause of the disease, and then receive targeted treatment from the doctor.