Stage III breast cancer is divided into stages IIIA, IIIB, and IIIC. In stage IIIB, the tumor may be any size and cancer (1) has spread to the chest wall and/or the skin of the breast; and (2) may have spread to axillary (under the arm) lymph nodes that may be attached to each other or to other structures, or the cancer may have spread to lymph nodes near the breastbone.