INFORMATION ON SENTINEL NODE BIOPSY
Sentinel Node Biopsy procedure as filmed for the RPA show in Australia.
The sentinel lymph node biopsy procedure involves three steps:
1. A lymphoscintogram
2. Intraoperative lymphatic mapping with blue dye and a gamma probe
3. Selective biopsy of lymph nodes identified as “sentinel” nodes.
These are explained below.
LYMPHOSCINTOGRAM
This is a nuclear medicine scan and is also referred to as a “lymphatic drainage scan”
(or a mapping test). This procedure is usually done the day before your operation or the morning before an afternoon operation. You do NOT have to fast (starve) before this test.
Typical Lymphoscintogram showing a Sentinel Node in the left groin.
Why is this test needed?
The purpose of the test is to accurately identify the location of the lymph nodes that drain the skin around the melanoma. This regional lymph node field might be at risk for containing metastatic disease.
How is it done?
A tiny dose of radioactive tracer is injected into the skin around the site of the primary melanoma. The tracer moves through the skin’s lymphatic channels and special scans are performed to determine the regional lymph node area to which drainage occurs. Scans are done immediately and 2-3 hours later. Although the tracer is radioactive, there is no significant risk to you from its use. Firstly because the dose is so small and secondly because it loses its radioactivity very quickly. The location of lymph nodes identified as “sentinel” nodes – the first nodes on the lymph drainage pathways – will be marked on the skin with indelible ink either in the form of little crosses or tattoos. If crosses have been marked on your skin, please try NOT to wash them off. This test cannot be done as accurately after you have had a wide local excision because the surgery will disrupt the natural lymph drainage pathways from the melanoma site.
Sentinel node theory.
Are there any side effects?
The side effects which may be associated with this scan are slight pain at the injection site during and shortly after the injection – the injections will sting less than the local anaesthetic you had when the melanoma was removed. You may also experience some redness at the injection site for an hour or two afterwards.
INTRAOPERATIVE LYMPHATIC MAPPING PROCEDURE
This procedure is performed in the operating theatre under a General Anaesthetic. A blue dye called Patent Blue V is injected into the skin around the site of the primary melanoma. The blue dye is rapidly absorbed into the lymphatic channels and moves to the regional lymph nodes. The blue colouring will assist in identifying the sentinel lymph nodes more easily. A Gammaprobe or giga counter is also used to identify the “hot” or radioactive sentinel node.
Sentinel node biopsy-blue node. Gammaprobe.
Are there any side effects ?
This procedure may be accompanied by discolouration of the injected skin and discolouration of the lymphatic channels leaving the injection site. But, this discoloured tissue is normally removed completely as part of the wide local excision procedure. There may be discolouration of the urine lasting no more than 48 hours. There is a possibility of allergic reaction, although this is very rare.
After the intraoperative lymphatic mapping procedure is performed, the selective lymph node dissection will be done. This consists of removing those lymph nodes which are first in line in the regional lymph node site and therefore the most likely to contain disease if it has spread. The test does not mean the melanoma has spread but simply identifies the at risk nodes.
SENTINEL NODE BIOPSY
The sentinel node biopsy is performed in the operating theatre at the same time as the wide local excision (the surgical removal of additional skin and tissue around the site of the primary [original] melanoma). An incision is made in the regional lymph node area(s) identified by the pre-operative lymphoscintigram. Blue and “hot” sentinel node(s) which are identified will be surgically removed and sent to the Pathology Department for examination. If melanoma cells are found to be present in a sentinel lymph node when the pathologist examines it, it will be recommended that a complete lymph node dissection, which is the removal of all the lymph nodes in that region, be performed within 4-6 weeks.
Are there any side effects ?
The side effects which might accompany a sentinel node biopsy may include the following.
1. Pain and / or discomfort at the site of the incision
2. Loss of sensation in and around the site of the incision as well as in the area immediately adjacent to this site.
3. Occasionally a little fluid may collect at the incision site which might be accompanied by local infection.
4. Occasionally some swelling of the limb or area nearest the incision site.
COMPLETE LYMPH NODE DISSECTION
This operation is performed if you have had a sample of lymph nodes removed and one of those nodes contained melanoma cells.
What is it?
A complete lymph node dissection is the surgical removal of all the lymph nodes in a specific region (neck, armpit or groin).
What are the side effects?
The side effects which might accompany a complete lymph node dissection may include the following.
- Swelling in the limb (lymphoedema) or area nearest the dissection site.
- Loss of sensation in and around the site of surgery as well as in the areas immediately adjacent to the operative site. Some degree of loss of sensation maybe permanent.
- Distortion of the natural anatomy in the operative site. This is a consequence
of surgery which cannot be totally avoided, but which your surgeon makes every attempt to minimise without compromising the effectiveness of the surgery.
- Increased susceptibility to infection in the involved limb if injury occurs. This will require more attention to skin cuts or abrasions in the involved area in future.
Prepared by Mr Richard Martin (MBChB, FRACS, MS), Cutaneous Surgical Oncologist. MU