Greenish discharge from nipple

My wife has noticed a greenish-black, apparently non purulent discharge from right nipple during process of pumping breast. Third child was just delivered. She has contacted her Dr. What are possible tumors or conditions that could be related?

[CCF-RN,MSN-rf]

Dear mark o: A small number of women may experience a bloody nipple discharge in the first few days after delivering and this condition (sometimes called "rusty pipe syndrome") should resolve on its own. A persistent abnormal discharge may be caused by a papilloma which is a benign growth in the ducts of the breast.  While cancer is a less common cause of abnormal nipple discharge during lactation, your wife is doing the right thing in contacting her physician.