Sentinel node biopsy is a technique to determine the status of the axillary lymph nodes without performing a full axillary dissection. The tumor site is injected with a radio-isotope and/or blue dye. This is tracked into the sentinel node, which is the first lymph node in the body to come in contact with cancer cells as they leave the primary tumor. The sentinel node is then removed.
If there is no breast cancer found in the sentinel node, no further nodes may need to be removed. If breast cancer is found, then more lymph nodes will need to be removed. Minimal node removal can save a woman from a condition known as lymphedema, a painful swelling of the arm.