A melanoma is a highly malignant tumour of the skin, which has a tendency to metastasize or spread widely and rapidly. Except for cancer of the lung, melanoma has the highest morbidity of all cancers. However if it is detected early the outcome of treatment is usually good; if not, it is invariably a fatal condition.
It used to be thought that all melanomas occurred in preexisting moles. The majority of melanomas, however, appear on blemish-free skin, with only about 25 per cent arising from moles.
Australia has the highest incidence of melanomas in the world. Approximately 3500 melanomas are expected to be diagnosed this year in Australia alone. In Queensland, where the majority of cases are found, the annual incidence has doubled from 16 per 100 000 population in 1966 to 33 per 100 000 in 1977. Since 1936, there has in fact been a six-fold increase. This reflects a world-wide trend.
The cause of the melanomas is unknown. However several important observations throw some light on possible causative factors. Genetic studies show that people of Celtic origin, such as the English and Irish (particularly those people with red hair, fair skin and blue eyes), are far more likely to develop a melanoma. The tumour is most uncommon in black races. Hormonal factors also appear to be involved, as females are more prone than males. Furthermore the tumour is extremely rare before puberty. Environment, as you may expect, plays an important part in the development of melanomas. There is considerable evidence that prolonged exposure to sunlight plays a central role in determining the frequency of melanoma. The closer to the Equator, the higher the incidence. This is as true in Europe and America as it is in Australia, where the incidence of melanoma in Queensland is greater than in the southern states.
The earth’s surface is partially protected from the sun’s ionizing radiation by a layer of ozone. This ozone layer is thinnest at the Equator and thickest at the Poles. Over recent years it has, however, been decreasing in thickness, due to the increased use of fluorocarbons. These gases have their sources in industry, car exhausts, spray packs, and supersonic aircraft. Also, at times of increased sunburst activity, there seems to be a concomitant increase in the frequency of melanoma.
The majority of melanomas in males are found on the back, and in females on the leg. However there is an increasing tendency to develop them on the head and neck. There seems little doubt that this distribution, and the increased incidence, must be related to changing fashions and values. Years ago both sexes wore far more protective clothing, in the form of long sleeves, skirts, and hats. Nowadays the quest is for the beautiful brown body. Consequently, the less clothing worn and the more holidays taken in the sun, the more successful you will appear in this quest. Equally, the more likely are your chances of developing this killer disease.
Since a quarter of all melanomas arise from a preceding mole, it is important to know which characteristics in a mole should arouse suspicion. One of the earliest signs of trouble may be an unusual tingling or itchiness in a normally symptomless mole.
Any colour change is suspicious. This may be a darkening, lightening, or simply a variation or irregularity in colouration. A red ring or inflammation around a mole should also be heeded. Similarly, any significant change in shape is important. This may be increased nodularity, enlargement, extension at one side, or ulceration. Obviously if a new ‘mole’ appears well after adolescence, then it should also be viewed with suspicion.
If your doctor suggests a biopsy of a suspicious mole, do not hesitate to have this done. It does not affect the course of the tumour, whether the biopsy is partial or complete. The important thing is to act quickly. When such changes as mentioned above are heeded and medical attention sought, the prognosis is infinitely better than if they go unrecognized or are ignored.
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