The extrusion of clear fluid from the breast is a very common phenomenon in clinical practice, and the common causes are as follows: 1. physiological factors, usually mostly during pregnancy or a short period of time after the end of lactation will extrude normal milk-like fluid, which may gradually improve over time; 2. pathological factors, including common diseases that cause nipple overflow, the main reasons considered are breast ductal dilatation, intraductal papilloma and mammary gland The main reasons for this are cystic hyperplasia, and more specific types of malignant tumors of the breast, all of which can lead to the extrusion of clear liquid and nipple overflow. Patients should pay close attention to this condition and identify the cause of the problem by doing breast ultrasound, ductoscopy or pathological smear of the clear fluid to clarify the cause and carry out systematic and standardized treatment according to the cause.