Mr. Andy Pay FRCS (Plast), Consultant Plastic Surgeon
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The internationally recognised standard of care for a lesion which might be a possible melanoma is initial (or “primary”) excision with a narrow margin (usually 2mm). It is vitally important that the lesion is excised with this narrow margin such that the entire lesion can be presented to the Pathologist for assessment. One of the most important prognostic factors in the management of melanoma is what is known as the Breslow Thickness. This is a physical measurement in millimetres of how far down through the skin the tumour has grown. The thicker the tumour is, the higher the risk of problems from the Melanoma. As the management of Melanoma is generally dependent on this measurement, this is why it is vital to present the entire full thickness of the entire lesion for the Pathologist. Punch biopsies and shave excision are generally best avoided where there is any possibility that the lesion might be a Melanoma.
Secondary (Wide Local) Excision
Once the lesion has been analysed in the laboratory, the Breslow Thickness will now be known. Having retrospectively reviewed the outcomes of patients wth a diagnosis of Melanoma, it is now generally recognised that many patients would have further problems from their melanoma if no further action is taken at this stage. The rates of local recurrence historically were reported at between 30 to 50% as generally nothing further was done at the primary site. This worrying fact led to multiple trials over the last 30 years which have given us guidance in how best to reduce this risk by excising additional tissue from around the biopsy site. Margin trials have been of immense value in guiding clinicians in how much additional tissue to resect in what is known as a Wide Local Excision. The general principle is that more tissue is removed the thicker the primary tumour, because the higher the Breslow Thickness, the higher the risk of local recurrence.
Melanomas of certain thicknesses have a pre-disposition to spread by utilising the lymphatic system. This comprises two main constituents; Lymphatic Channels and Lymph Nodes.
The channels are microscopic conduits which are situated within the upper layers of the skin and drain fluid from the periphery of the body towards the centre. Melanoma cells can use this network to move through the tissues and cause problems elsewhere.
The anatomical arrangement of the lymphatic system means that the microscopic channels eventually drain into lymph nodes. These are anatomical structures which are in groups that are located in the groin (inguinal), armpit (axilla) and in the head and neck (cervical).
Apart from their role in infection and inflammation, they act as microscopic filters and as a result, melanoma cells become trapped within the lymph node which is the first encountered from the primary site, the Sentinel Node.
Sentinel Node Biopsy
This is the investigation to find the lymph node(s) that may contain small cellular deposits of melanoma which have travelled along the lymphatic channels from the primary site. It is reserved for patients where there is no clinical evidence of an enlarged lymph node in the relevant drainage basin. These patients are known as “Clinically Node Negative“. The investigation was pioneered by Mr D Morton in the late 80’s and early 90’s, and is the best method we currently have of assessing whether melanoma has spread to the local lymph nodes. The principle is that by using a low dose of a radio-active isotope and a blue dye which are both injected into the biopsy scar, the pathway that the melanoma cells might have taken can be traced. Both agents are concentrated in the first lymph node they encounter, which is the sentinel node. Through a small skin incision this node is then removed and sent for laboratory assessment. It is accurately localised by visual clues (it is stained blue by the dye) and audible clues (it can be detected by an instrument which is a type of Geiger counter). There are sometimes multiple nodes, and these can be in different drainage basins particularly if the primary site is near the midline of the trunk. This investigation gives a lot of information and helps clinicians advise on the behaviour of the melanoma, gives prognostic information and helps direct further clinical management.
I have personally performed over 500 Sentinel Node Biopsies over the last 20 years, with no “False Negatives” and a positivity rate of 16%. My complication rate for this surgery is less than 1%, which is comparable with published international standards of practice. I have remained compliant with the National Guidelines for Completion Dissections for the Axilla and Inguinal regions and am one of only 4 surgeons formally recognised and approved to perform these operations within the Thames Valley Cancer Network.
Melanoma of sole of foot injected with Blue Dye
Dermal lymphatics visible coursing away from the injection site
Sentinel nodes visible via Incision through skin
The results from the Sentinel Node Biopsy will either be Negative (c 80%) or Positive (c 20%). In the former situation, where there is no evidence of nodal metastatic spread, this is clearly good news and reassuring. Generally no further investigations or interventions are required as a Negative result means there is no evidence that the melanoma has spread to the next most likely place. The patient will have Stage 1 or 2 disease. The risk of further problems, however, remains related to the original Breslow thickness of the primary and therefore patients are kept under close surveillance. The duration and frequency of surveillance is related to the relative risk associated with the primary Melanoma. During surveillance appointments, patients will be taught how to monitor their own skin population of moles , but also how to examine their own relevant lymph node drainage basin. Also importantly, advice is given on Sun Protection with hats, clothing and sun protection factors.
In the converse situation where the Sentinel Node is Positive, this means that the melanoma has metastasised to the lymph nodes and is termed Stage 3 disease. At this point, most patients will have a staging CT scan, to find out whether there is any evidence of melanoma anywhere else in the body. From this point there are a number of possible pathways. Historically, up until recently, the general consensus amongst Melanoma Specialists was to perform a further surgical procedure to remove the remaining lymph nodes from the relevant nodal group where the Positive Sentinel Node was sampled. This is a more major procedure with a higher rate of recognised complications, ranging from wound healing issues to the development of Lymphoedema (an accumulation of fluid within a limb). Some of the side effects and complications of this Completion Dissection can be protracted and potentially life changing. It was partly because of this and also the advent of new possibilities within Melanoma therapy, but also an analysis of long term surgical outcomes that have led to Specialists feeling less compelled to advise further surgery as the best option.
The last few years, recent advances in the field of Melanoma Medical Oncology have significantly improved the management of patients with advanced Melanoma, particularly Stage 4 disease. Immunotherapy agents have been developed which have produced significant benefits in patients where previously there had been no treatment available at all. Due to my close liaison with colleagues in the Skin Cancer Multi-Disciplinary Teams, I am able to direct patients with advanced Melanoma to the correct Oncology Specialists to discuss possible ongoing further additional treatments and interventions.