Cancer that has spread from where it began in the breast to surrounding normal tissue. The most common type of invasive breast cancer is invasive ductal carcinoma, which begins in the lining of the milk ducts (thin tubes that carry milk from the lobules of the breast to the nipple). Another type is invasive lobular carcinoma, which begins in the lobules (milk glands) of the breast. Invasive breast cancer can spread through the blood and lymph systems to other parts of the body. Also called infiltrating breast cancer.