Sentinel Node Biopsy

The sentinel node is the lymphatic node which receives drainage directly from the primary tumour. A sentinel node biopsy involves identifying the sentinel node or nodes, removing the node/s and sending them to a pathology lab for testing.

The Clinical Practice Guidelines for the Management of Melanoma in Australia and New Zealand state:
“Sentinel node biopsy is an important prognostic factor for melanoma, but that there is debate about its use in treatment. Sentinel node biopsies should be considered in patients with primary melanomas greater than 1mm thick or Clack level IV, who want to be as informed as possible about their prognosis”.

The first of the three steps in a Sentinel node biopsy is called a lymphoscintogram . This step is performed to accurately identify the location of the lymph nodes which drain the skin around the melanoma. A lymphoscintogram is also referred to as a “lymphatic drainage scan” or mapping test and is usually done on the day before your operation (if you are having your operation in the morning), or on the morning of your operation (if your operation is taking place in the afternoon). You do not need to fast for this test. During this procedure a tiny dose of radioactive tracer is injected into the skin surrounding the melanoma. The doctor administering this test may then do a small massage of the site. The tracer will move from the injection site and travel to your lymph nodes. Scans are done while this is happening which will reveal which node/s is directly draining the site where the melanoma is located. The location of the lymph nodes will be marked in ink with a X. Some people are understandably nervous about the injection of radioactive tracer into their skin. It is therefore important to be aware that there is no significant risk to you from the tracer. The dose used is very small and the tracer loses its radioactivity very quickly. You may feel some stinging at the injection site and may also have some redness at the injection site for an hour or two after this procedure.

The second step is called an intraoperative lymphatic mapping procedure and is performed in the operating theatre under general anaesthetic (i.e. you will be “asleep” for this). A blue dye (called Patent Blue V) is injected into the skin around the site of the melanoma and moves along the lymph channels to the lymph nodes. The blue dye assists your Surgeon in identifying the Sentinel node/s. A gamma probe or giga counter picks up and identifies the “hot” or radioactive sentinel node. You may notice some blue discoloration of the skin – however the discoloured tissue is usually removed as part of the procedure. There may be some discoloration of the urine for up to 48 hours following the procedure. There is also a chance of an allergy to the dye – however this is very rare.

The third step is the removal of the sentinel node/s. Your surgeon will make an incision into the lymph node area (identified by the lymphoscintogram) and the blue or “hot” sentinel nodes/s will be surgically removed and sent to the pathology lab for examination. You may notice some pain or discomfort at the operation site and you may experience loss of sensation around the site of the incisions well as the area immediately adjacent to the site. Occasionally, there can be some swelling of the limb or area nearest to the incision site. As with any operation there is a risk of infection.