Melanoma is the eighth most common malignancy in the UK. In 2003, there were 8114 new cases and 1777 deaths. Incidence rates have increased every year for the last three decades, faster than that of any other major cancer, making melanoma an increasing public health concern. Despite this, increments in mortality have been smaller, and melanoma accounts for only 1 - 2% of total cancer deaths in the UK. One-third of patients are under the age of 50, and approximately 15 years of life are lost for each death, placing melanoma amongst the top five cancer causes of lost life-years.
In the UK, the incidence of melanoma has more than tripled over the last 25 years to age-standardized rates of 11.1 per 100 000 in men and 12.6 per 100 000 in women in 2003. The increase in incidence has been greatest for melanoma under 1 mm in Breslow thickness. It has been proposed that this increasing trend may be an epiphenomenon attributed to earlier detection, better surveillance and changes in diagnostic criteria. However, available evidence suggests much of the rising incidence is real.
Mortality rates have also significantly risen over the last 25 years, but at a much slower pace as tumours less than 1 mm in Breslow thickness have a good prognosis. In contrast to incidence, mortality is greater in men, with male deaths outnumbering female deaths almost twofold. The rise in melanoma mortality has been greatest among men aged more than 65 years, who present late with thick (more than 4 mm in Breslow depth) advanced tumours that have a poor prognosis. Reasons for this include the tendency for melanoma to be located on the back in males where they are hard to see, lack of self-examination and a tendency for not reporting changing moles.
The most common types of primary cutaneous melanoma - superficial spreading melanoma, nodular melanoma and lentigo maligna melanoma - are cancers of whiteskinned people and are associated with a number of well-established risk factors . Rarely, melanoma occurs on the palms and soles, nail apparatus and genital and sinonasal mucosa. These rare subtypes are equally common in all ethnic groups irrespective of skin colour, and are of unknown aetiology.
Certain heritable traits such as red hair and freckles are associated with an increased relative risk for melanoma of about 3. The most potent risk factor, however, is the presence of increased numbers of moles (benign melanocytic naevi) and the presence of bigger moles with an irregular or ill-defined edge, known as atypical moles. Moles are acquired proliferative lesions, which appear from early childhood until mid-adult life, when they start to reduce in number. Individuals living in hot countries, such as Australia, have more moles then those living in Europe, implying that they are induced by sun exposure. However, twin studies provide good evidence that the number of moles is also determined genetically.
As large numbers of moles are a risk factor for melanoma, it is hypothesized that that mole genes are also low-risk melanoma susceptibility genes. Two per cent of the UK population have the Atypical Mole syndrome, which is a phenotype associated with both large numbers of moles (more than 100 moles more than 2 mm in diameter) and moles which are atypical (being larger than 5 mm in diameter with an irregular shape and colour). Patients with the Atypical Mole syndrome have a significantly increased risk of melanoma.
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