In some cases, the cancer is too large to be removed by lumpectomy. In these situations, removal of the breast along with the lymph nodes in the armpit (axilla) that drain the breast, is required. This procedure is called modified radical mastectomy (MRM). The results of mastectomy for breast cancer depend on the stage of the cancer, the tumor size, and whether there is cancer in the lymph nodes.

Chemotherapy is often administered after surgery for patients with cancer involving the lymph nodes.