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Melanoma is the least common of the three main types of skin cancer (the other two being squamous cell carcinoma and basal cell carcinoma) and accounts for less than three per cent of all skin cancers. Melanoma is, however, generally more serious than either of the more common types, although it is treatable if it is detected early enough. The number of cases of melanoma has increased rapidly over the last 40 years and is continuing to do so.
Residents of certain countries are at greater risk of developing melanoma than others. For example, the condition is almost ten times more common in Australia and New Zealand than it is in Europe. It has long been known that this geographical distribution occurs because sunlight is probably the most important factor in the development of melanoma - 75% of tumours occur on sun-exposed skin, and fair skinned people are at much greater risk than those with dark skin. There are also reports of hereditary skin cancer, but these are relatively rare.
Melanomas get their name from the cells from which they develop - melanocytes. These are the pigment1-containing cells that give skin its colour. For this reason, most melanomas are black or brown, although they can occasionally lose their colour, appearing pink or red. Melanomas are divided into three main categories:
Together, these three types make up around 90% of all melanomas. The remaining ten per cent are made up of other types, such as those arising from mucous membranes4, the palms of the hands or soles of the feet.
Treatment of Melanoma
If a melanoma is still in situ, surgical removal is the easiest and most effective way of treating it. The surgeon removes the tumour and a certain amount of surrounding skin, to be certain of taking all cancerous cells. As surgical techniques have advanced, the amount of skin that it is necessary to remove has become less and less, which means that the scar is as small as possible. For small tumours, surgery can be done in an out-patient clinic or GP's surgery using a local anaesthetic. Larger tumours require deeper and wider surgery, and a skin graft from another part of the patient's skin may be necessary.
If the melanoma has invaded deeper into the skin, there is a chance that it will have spread ('metastasised') to other parts of the body. The first locations reached by spreading tumour cells are usually the lymph nodes5 nearest to the original tumour. If enlarged lymph nodes near the tumour can be felt, they will be removed surgically and examined for signs of cancer. If no enlarged lymph nodes can be felt, there are two possible options, both of which are equally acceptable and depend on the opinion of your physician. Some prefer to remove all lymph nodes around the tumour as a preventative measure, although there is no definite evidence that this is worthwhile. If the physician chooses not to remove the lymph nodes, the patient returns to the surgery for regular check-ups.
For many years it was thought that radiotherapy was of no use in the treatment of melanoma, and melanomas are generally resistant to radiation. More recently there have been some reports of the successful use of radiation to treat the disease, particularly tumours on the arms or legs where a high dose of radiation can be given without the risk of damaging the internal organs.
If the melanoma has metastasised from its original location, chemotherapy is used to try to kill the cancer cells wherever they reach within the body. The most commonly used drug is dacarbazine, although several others are used, often in various combinations.
There have been a few rare cases in which a melanoma has disappeared without treatment. This is thought to be due to an immune response by the patient's body, and has led many researchers to investigate 'immunotherapy' - methods of enhancing the body's immune system to allow it to cope more easily with a tumour. This research is, however, still in the early stages. It is hoped that such techniques may one day make it possible to develop vaccines against melanoma, although these are, unfortunately, a long way off.
Melanoma is still the most serious of the main types of skin cancer, but things are getting better. Recent advances in all areas of therapy mean that treatment is improving all the time, while public education on sensible sun exposure should mean that fewer people develop these tumours.
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