What is spontaneous nipple discharge?

Spontaneous nipple discharge is fluid leakage from one or both breasts that occurs without any stimulation, such as by squeezing the nipple. Spontaneous nipple discharge may signal a medical problem, particularly if:

• It occurs only in one breast.
• The discharge is bloody or pink, or gray or otherwise discolored.
• It occurs in a woman age 40 or older.
• It occurs in a woman who is neither pregnant nor nursing. 
• It is accompanied by a lump that can be felt, a retracted nipple, or breast skin that is dimpled, swollen and/or red.
• It occurs in a boy or a man.

Common causes of spontaneous nipple discharge are breast lumpiness (fibrocystic breasts), infection, dilated milk ducts or a benign tumor in a milk duct. Breast cancer causes fewer than 10 percent of cases of spontaneous nipple discharge.