Sentinel Lymph Node Mapping

David Arbutina, M.D., FACS

To determine the stage of a cancer, lymph nodes are removed to see if the cancer cells have the ability to grow outside the tissue of origin.  If cancer cells are found growing in the lymph nodes, it signifies that the cancer can grow in other organs.

Historically, lymph nodes were removed based on anatomic location requiring extensive surgery with possible adverse effects.   Removing only the first lymph nodes which drain a cancer site, known as a sentinel lymph node biopsy, is much less likely to cause problems while still answering the important questions.

To find the sentinel node, a tracer of either blue dye, radioactive sulfur colloid or both are injected near the tumor.  These first nodes can then be found using a Geiger counter or surgically exposing the area.  The radioactive tracer can be injected up to 24 hours prior to surgery.  The blue dye is usually injected in the OR at the time of surgery.   Frozen section of the lymph node for immediate pathologic assessment is no longer necessary.

Today, local anesthetic is mixed with the tracer to prevent the burning pain which was the major patient complaint about the procedure.  Studies have shown local does not alter the accuracy of the test.

A positive sentinel node with breast cancer is now frequently treated with only radiation to complete the therapy of the remaining nodes.  However, with melanoma, a positive sentinel node still requires the extensive removal of adjacent nodes but even this practice is being questioned by ongoing research.