Dear horses1016: Without evaluation, it is not possible for us to speculate on what this may be and why. Our recommendation is that you might consider seeing a medical breast specialist who can evaluate this for you. An evaluation would include breast examination, review of the pathology from the surgery, review of the mammogram and analysis of the fluid, if applicable. Nipple discharge is not uncommon, particularly when the nipple is squeezed. However, if this is infection, it may require a different management approach.