Sentinel lymph node biopsy is a procedure used to determine whether cancer has spread to the lymph nodes. It involves injecting a dye or radioactive substance near the tumor site. The first lymph node to which the dye travels is called the sentinel lymph node. This node is then removed and examined for cancer cells. If no cancer is found, it is unlikely that the cancer has spread to other lymph nodes, potentially sparing the patient from extensive lymph node removal.
