Sentinel node biopsy is a surgical procedure used to determine if cancer has spread beyond a primary tumor into your lymphatic system. A sentinel lymph node is defined as the first lymph node to which cancer cells are most likely to spread from a primary tumor.
Sentinel node biopsy involves injecting a tracer material that helps the surgeon locate the sentinel nodes during surgery. The sentinel nodes are removed and analyzed in a laboratory by a pathologist. If the sentinel nodes are free of cancer, then cancer isn't likely to have spread and removing additional lymph nodes is unnecessary.