Sentinel Lymph Node Biopsy

The lymphatic system will make every effort to protect the body by trapping cancer cells within its lymph nodes if they have spread from the original cancer site. The first node to receive lymphatic drainage from a tumor is called the sentinel lymph node. Taking a biopsy of the sentinel lymph node will allow physicians to determine their next course of action.

The Procedure

SLNB is done prior to the removal of the main tumor. It is a two step process which involves first identifying the sentinel lymph node followed by its removal and microscopic evaluation.

Identifying the sentinel lymph node

The process begins in the Nuclear Medicine department of a radiology facility. The radiologist injects a radioactive substance near the tumor. After 15 – 60 minutes, the body is scanned with radiation detectors to show how the substance travels through the lymphatic system. Images of the scan are then taken by the patient to their scheduled biopsy.

Removal and Evaluation of the Sentinel Lymph Node

The surgeon will use the Nuclear Medicine images taken at your previous scan, as well as a special radiation-detecting probe (Gamma probe) to identify the greatest concentration of the radioactive tracer. (This is the same fluid that was injected into the tumor site during the imaging process). The lymph node with the greatest amount of radioactive tracer is the sentinel lymph node. 

Some surgeons choose to modify the sentinel lymph node identification process by injecting a dye called methylene blue into the tumor. The dye will travel through the lymphatic system in the same manner as the radioactive tracer, turning up in the sentinel lymph node first. This serves as an additional point of reference for physicians to use in combination with the imaging and Gamma probe.

Once the the surgeon identifies the lymph node, it is removed. The lymph node is sent to a pathologist for specialized testing to identify cancer cells.