Before radiation therapy begins, some or all of the underarm lymph nodes are usually removed to determine if the cancer has spread beyond the breast. If all of the lymph nodes are removed, the surgery is called axillary dissection; if only some of the lymph nodes are removed, it is called axillary sampling. Other tests such as bone and liver scans may also be done to provide your doctor with valuable information needed to plan further treatment. This process is known as "staging" the disease.
Hospital procedures and policies vary, but there are a number of things you can probably expect to have happen when you check in for lymph node surgery.