Stage III breast cancer is divided into stages IIIA, IIIB, and IIIC. In stage IIIA, (1) no tumor is found in the breast, but cancer is found in axillary (under the arm) lymph nodes that are attached to each other or to other structures, or cancer may be found in lymph nodes near the breastbone; or (2) the tumor is 2 centimeters or smaller and cancer has spread to axillary lymph nodes that are attached to each other or to other structures, or the cancer may have spread to lymph nodes near the breastbone; or (3) the tumor is larger than 2 centimeters but not larger than 5 centimeters and cancer has spread to axillary lymph nodes that are attached to each other or to other structures, or cancer may have spread to lymph nodes near the breastbone; or (4) the tumor is larger than 5 centimeters and cancer has spread to axillary 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. 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 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. In stage IIIC, there may be no sign of cancer in the breast or the tumor may be any size and may have spread to the chest wall and/or the skin of the breast. Also, cancer (1) has spread to lymph nodes above or below the collarbone, and (2) may have spread to axillary lymph nodes or to lymph nodes near the breastbone. In operable stage IIIC, the cancer is found (1) in ten or more axillary lymph nodes; or (2) in the lymph nodes below the collarbone; or (3) is found in axillary lymph nodes and in lymph nodes near the breastbone. In inoperable stage IIIC, the cancer has spread to the lymph nodes above the collarbone.