Cancer that has grown beyond its site of origin into neighboring tissue. Invasive does not imply that the cancer has already spread outside the breast. Invasive has the same meaning as infiltrating. Understanding Breast Cancer
Cancer that has spread beyond the area it originally developed in, to involve adjacent tissues. For example, invasive breast cancers develop in milk glands (lobules) or milk passages (ducts) and spread to the adjacent fatty breast tissue. Some invasive cancers spread to distant areas of the body (metastasize), but others do not. Also called infiltrating cancer. ( See also invasive ductal carcinoma, invasive lobular carcinoma).