There are so many reasons why lactating breasts can have lumps. Why not have a needle aspiration (My medical knowledge is limited but at a local conference a surgeon talked in depth about needle aspirations.) If it is cancerous a granular substance is obtained which requires further investigation. More than likely a milky substance would be obtained or perhaps it could be an abscess in which case greenish black fluid is obtained. Ultrasound can help in some cases either to disperse the lump or to perhaps show if it is a galactocele. The Breastfeeding Answer Book has some useful information ( p426-427 ) about breast lumps. Ruth Bacon IBCLC Ontario