Suddenly milk can be squeezed out of the breast is generally a manifestation of milk overflow, may be caused by hyperprolactinemia, breast hyperplasia, breast cancer and other diseases. 1. hyperprolactinemia: hyperprolactinemia refers to the abnormal elevation of serum prolactin, which is mainly manifested in amenorrhea, lactation, menstrual disorders, infertility, hypogonadism, headache, visual impairment and other symptoms, breasts can suddenly squeeze out of the milk may be caused by hyperprolactinemia. 2. Mammary hyperplasia: Mammary hyperplasia is a common benign breast lesion, which mainly manifests as breast pain, breast nodules or lumps, and some of them can be combined with nipple discharge and other symptoms. 3. Breast cancer: Breast cancer is a malignant tumor formed by uncontrolled proliferation of epithelial tissues in breast ducts or lobules, and patients may have local symptoms such as breast lumps, nipple and areola changes, breast skin changes, nipple discharge and so on. It is recommended that patients seek timely medical examination to clarify the cause of the disease and then carry out targeted treatment, pay attention to monitoring the condition in life, and regular review.