A lymph node is a rounded body of lymph tissue found in certain places in your body. Lymph nodes produce lymphocytes and monocytes (white blood cells) and act as a filter keeping bacteria and cancer cells from entering the blood stream. A sentinel lymph node is an enlarged lymph node where cancer cells have spread.
Sentinel node biopsy is a technique which helps determine if a cancer has spread (metastasized). The concept of the “sentinel” node, or the first node to drain the area of the cancer, allows a more accurate staging of the cancer and leaves unaffected nodes behind to continue the important job of draining fluids. To perform the procedure, patients are injected with a small amount of traceable blue dye around the cancer (or tumor) which then travels to the sentinel nodes. A sentinel node is identified by the blue color and by using a very sensitive Geiger counter in the operating room. The sentinel node is then removed and examined under the microscope for cancer cells. If the sentinel node does not contain cancer cells, it is unlikely that there are any other lymph node that contain cancer.