A sentinel lymph node is defined as the first lymph node to which cancer cells are most likely to spread from a primary tumor. A sentinel lymph node biopsy (SLNB) involves identifying, removing, and examining the sentinel lymph node to determine whether cancer cells are present. A positive SLNB result indicates that cancer is present in the sentinel lymph node and may be present in other nearby lymph nodes (regional lymph nodes) and, possibly, other organs.
A radioactive substance, a blue dye, or both are injected near the tumor to locate the position of the sentinel lymph node, and, once the sentinel lymph node is located, the surgeon makes a small incision and removes the node. The node is then checked for the presence of cancer cells by a pathologist. The surgeon may remove additional lymph nodes if cancer is found, either during the same biopsy procedure or during a follow-up surgical procedure. SLNBs may be done on an outpatient basis or may require a short stay in the hospital, and are usually done at the same time the primary tumor is removed. The procedure can also be done either before or after removal of the tumor.