 The concept of sentinel lymph node surgery is to determine if the cancer has spread to the very first draining lymph node (called the "sentinel lymph node") or not.If the sentinel lymph node does not contain cancer, then there is a high likelihood that the cancer has not spread to any other area of the body.The concept of the sentinel lymph node is important because of the advent of the sentinel lymph node biopsy technique, also known as a sentinel node procedure.