This is one of the most recent and exciting advances in staging for colon and rectal cancer. At the time of surgery, a vital blue dye is injected into the tumor and the first lymph nodes draining the tumor can be identified. This allows the pathologist to perform a more comprehensive and focused examination of these lymph nodes to detect metastasis. In a recent study of 200 patients, sentinel lymph node mapping enabled detection of 15% more patients who had lymph node metastases. By detecting spread of tumor to lymph nodes at an earlier stage than previously possible, patients who may not have been eligible for additional life-improving chemotherapy to now be eligible.