How does breast cancer spread into the rest of the body?

Circulation: Most breast cancers arise from the ducts or lobules of the breast. An invasive cancer breaks out of these structures and enters into the supporting tissue of the breast, where the lymphatics and blood vessels are found. The cancer cells may enter into these tubes and travel throughout the body.

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.

Lymphatics: Breast cancer spreads through your lymphatic system.