The enlargement of one side of the breast is likely to be related to congenital factors or breast hyperplastic diseases, and can be treated conservatively or surgically according to the specific situation. 1. Congenital factors: If the enlargement of one side of the breast is caused by congenital factors, if it does not affect the aesthetics, it can be left untreated; if the enlargement is more serious, surgery can be considered to remove the diseased tissue. 2. Breast proliferative diseases: Suffering from breast hyperplasia, breast cancer and other breast proliferative diseases may also lead to enlargement of one side of the breast. Breast hyperplasia, if there is no obvious clinical symptom, can be left untreated for the time being, and come to the hospital for regular checkups. Breast cancer can lead to enlargement of one side of the breast, need to cooperate with the doctor to receive surgery, radiotherapy, chemotherapy and other comprehensive treatment. If one side of the breast is enlarged, there may be other causative factors, so it is recommended to go to the breast surgery department of the hospital and receive treatment according to the cause of the disease.