What is a sentinel node and what is a false-negative sentinel node?

Morton's original definition of a sentinel node as the first lymph node to receive afferent lymphatic drainage from a primary tumor reflects the concept of stepwise spread of cancer through the lymphatic system. Several new definitions have been developed, based on surgical anatomy and on the technique that is used to find the node. The various definitions of a sentinel node are critically analyzed. Breast cancer surgeons use three different definitions of a false-negative sentinel node biopsy. The best definition appears to be based on the assumption that the procedure is truly positive if either the sentinel node or a suspicious node that is not radioactive or blue contains metastatic disease.