(1) Physiologic overflow: refers to overflow that is not due to breast disease. With the exception of lactation, these tend to be non-spontaneous bilateral nipple overflows and are secreted from multiple ducts. The color of the overflow is usually yellowish. Nipple irritation, sexual stimulation, application of exogenous hormones and certain sedative drugs may induce nipple overflow. (2) Pathologic overflow: refers to nipple overflow caused by disease. It is often unilateral and confined to a single duct. The most common colors are bloody, brown or purple-black. The most common causes of bloody discharge are intraductal papillomas, ductal dilatation, and mastal hyperplasia. About 3% to 10% of patients with breast cancer also have nipple discharge.