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Another way of evaluating lymph nodes is with an axillary lymph node dissection. During this procedure, most lymph nodes under the arm (generally 20 to 25) are removed and examined for evidence of cancer. Because more lymph nodes are studied, the doctor may have more evidence of whether the cancer has spread. However, this procedure can result in long-term complications or disabilities, including pain and numbness in the arm and lymphedema (excess fluid in the arm that causes swelling). Although some patients may experience side effects from SNB, these are usually milder than the side effects experienced after an axillary lymph node dissection.