Most nipple discharges are due to benign changes and are not a sign of breast cancer. When the discharge is spontaneous, clear or bloody, and the discharge is coming from one duct, it should be evaluated. This is accomplished by placing a tiny tube in the opening of the duct, through which a small amount of liquid dye is injected. A mammogram is then performed. The dye makes the duct visible on the mammogram, enabling the doctor to identify defects within the duct.