Fluid extrusion from the nipple may be caused by mastitis, ductal tumor of the breast, breast cancer and other diseases. 1. Mastitis: Breastfeeding mastitis is caused by milk stagnation and stimulation of bacterial infection. Non-breastfeeding mastitis may be caused by obstruction of milk ducts, infection, smoking, breast trauma and other factors, leading to the phenomenon of liquid extrusion from the nipple, accompanied by breast pain, redness and swelling and other symptoms. 2. Ductal tumor of breast: The clinical manifestations of intraductal papilloma of breast are mainly abnormal nipple fluid overflow and breast lump. Clinical manifestations of intraductal papilloma mainly include abnormal nipple discharge and breast lump. Unexplained abnormal nipple discharge is the first symptom in clinic, and bloody discharge is the most common, while a few are plasma discharge or both of them appear alternately. 3. Breast cancer: If the patient is affected by hormone, radiation, bad lifestyle, heredity and other factors, the long-term effect leads to mutation, cancer, development and metastasis of breast epithelial cells, resulting in the emergence of liquid extrusion from the nipple. At the same time, dilated ducts, breast hyperplasia, endocrine diseases (ovarian or pituitary tumors) and certain physiological conditions in women may also appear nipple discharge, which need to be carefully identified. It is recommended that the patient go to the hospital in time, under the guidance of the doctor, to carry out the relevant examination, according to the patient’s specific examination results, to take targeted treatment.