Nipple overflow refers to the active or passive outflow of fluid from the nipple during non-lactation, including nipple secretion of paste-like material. When diagnosing the etiology of nipple discharge, in addition to a detailed medical history and physical examination, careful observation of the nature of the discharge and whether it is uniportal or multi-portal should be performed, in addition to relevant ancillary tests to aid in the diagnosis. Nipple overflow with lumps is treated with reference to the diagnostic process of breast lump flow. 1. Bilateral overflow: Pregnancy test for women with possible pregnancy. (1) Positive pregnancy test For patients with a positive pregnancy test, which is a physiological nipple overflow, an obstetrician should be consulted and a routine obstetric examination should be performed. (2) Negative pregnancy test A negative pregnancy test is considered an endocrine test (serum PRL level and TSH level). When serum PRL>100ug/L, highly consider the possibility of prolactinoma (pituitary microadenoma); when PRL>200ug/L, most of them are prolactinoma; when PRL<100ug/L, mostly consider hyperprolactinemia; elevated TSH level is mostly seen in primary hypothyroidism. 2. Unilateral breast overflow or unilateral/bilateral porous clear water-like overflow (1) Age < 40 years, can be observed; or tell the patient to stop squeezing the breast, come to the hospital when the nature of overflow is found to change, and perform ductoscopy, mammography and ultrasonography if necessary. (2) Age ≥ 40 years old, you can mammography; or tell the patient to stop squeezing the breast and come to the hospital when the nature of the overflow changes, and perform mammography and ultrasonography, etc. if necessary. 3. Plasmacythematous, bloody, or plasmacythematous overflow: perform mammography + ductoscopy/mammography (ductoscopy preferred) (1) If there is a lesion on the ductoscopy/mammography, perform surgical biopsy and treatment. (2) No lesion on mammography/mammogram ① Mammography with BI-RADS grade 0-3: follow up for 3 months, still have overflow or persistent overflow and undergo mammography again, surgical treatment if mammography result is abnormal, liquid-based cytology (TCT) of milk duct flushing fluid if mammography result is not abnormal, surgical biopsy and treatment if test result is abnormal, further follow up if test result is not abnormal. If no abnormal results were found, further follow-up was performed. (ii) Mammogram with BI-RADS grade 4-5: surgical biopsy and treatment after a thorough examination and evaluation. (3) Hemorrhagic overflow: perform liquid-based cytology of ductoscopy flushing fluid, surgical biopsy and treatment for abnormal test results, and surgical biopsy for abnormal test results combined with clinical and other tests. (3) Hemorrhagic overflow in pregnancy: lactoscopy is feasible in the middle of pregnancy if necessary.