How are you? Breast abscess or painful collection of pus that forms in the breast may be caused by a bacterial infection or mastitis. The bacteria usually enter the breast through small cracks or breaks in the skin of the nipple or overgrowth of bacteria that can occur if stagnant milk collects in a blocked milk duct. The body's immune system tries to fight these bacteria and as the white blood cells attack these, some of the tissue at the site of the infection dies, creating a small, hollow pocket that fills with pus to form an abscess. Antibipotic management may be indicated. Take care and do keep us posted.