The sentinel nodes are the first few lymph nodes into which a tumor drains. Sentinel node biopsy involves injecting a tracer material that helps the doctor in locating the sentinel nodes during surgery. The sentinel nodes are then removed and analyzed in a laboratory.
If the sentinel nodes are free of cancer, then cancer is unlikely to have spread, so removing additional lymph nodes is not advised.
If a sentinel lymph node biopsy reveals cancer, the surgeon might recommend removing more lymph nodes.