Nipple discharge is a common symptom of breast disease. The incidence of nipple discharge in breast disease is second only to breast lumps and breast pain. It can be divided into physiological discharge and pathological discharge. Physiological discharge refers to the phenomenon of lactation during pregnancy and lactation, bilateral nipple discharge caused by oral contraceptives or sedatives, and unilateral or bilateral small amounts of discharge in postmenopausal women. Pathological discharge refers to natural discharge from one or more ducts on one or both sides under non-physiological conditions and unrelated to pregnancy and lactation, which can be intermittent or continuous from several months to several years. Nipple discharge mainly refers to pathological discharge.