It is believed to be of significant importance to document the spread of melanoma into draining lymph nodes. This information instructs the medical oncologist regarding the most appropriate chemotherapy or biologic therapy. 10 years ago, this information would be obtained by doing a complete removal of all lymph nodes draining the site of the primary melanoma. In addition it was felt that this might provide some therapeutic advantage by clearing any microscopic tumor which had spread to these lymph nodes. Unfortunately the complete removal of all lymph nodes leads to chronic problems with pain from the surgery site and swelling of the extremity that had previously been drained by those lymph nodes. This poor outcome led to the development of techniques which would be easier for the patient. Sentinel lymph node mapping is a way in which the principal lymph node which drains the tumor can be identified and sampled. If it contains melanoma, then more lymph nodes can be removed or appropriate chemotherapy or biologic therapy can be recommended.

The technique involves placing a small amount of radioactive tracer material and/or blue dye into the area surrounding the tumor. We then trace the dye to its first encounter with a lymph node (sentinel lymph node). Through a small incision we are able to excise that lymph node and have it examined under the microscope. If no tumor is detected in the lymph node, this predicts that in most cases that no residual microscopic tumor has spread to any lymph node in that region and therefore no further surgery is necessary. If tumor has spread to that lymph node, it may be reasonable to consider the removal of more lymph nodes.