3 Basic Ways. Breast cancer can spread in 3 basic ways - it can grow larger and larger, invading into the skin or muscle; it can invade into the blood vessels and then travel to other areas of the body (most commonly liver, lungs, bone and brain), and it can invade into the lymphatic vessels and travel to the lymph nodes under the arm and other areas of the body.
Circulation. Most breast cancers begin in the breast ducts, where milk is transported to the nipple. Invasive cancers break out of the duct and spread to the adjacent supportive tissue within the breast, where the lymphatics and blood vessels are found. These cancer cells may enter these vessels and travel anywhere in the body.