Written by epgonline.org - Last updated 29 May 2018
Although it is one of the rarer forms of skin cancer, melanoma is responsible for a disproportionate amount of mortality. Its incidence has been increasing over time, and is heavily linked to sun exposure. Figures from the World Health Organization suggest an annual incidence of 132,000 worldwide.
Melanoma is much more common in the Caucasian population, with skin subtype also conferring much greater risk – the fairer the skin, the more susceptible the person is to developing melanoma. With this in mind, it is unsurprising that the countries with the highest incidence of melanoma are those where pale skin predominates – this is particularly evident when linked with increased sun intensity. The burden of disease is highest in Australia and New Zealand, but remains significant in Europe (particularly Northern Europe) and the USA. Melanoma is possible in populations of African descent, but is rare – fair-skinned Americans are approximately 26 times more likely to develop the disease compared with black Americans.
Melanocytes are the pigment-containing cells of the skin that may become melanoma. The process is understood to be driven by ultraviolet radiation, with one or more blistering episodes of sunburn in childhood or adolescence doubling the risk of melanoma in later life. There is also an association with increased risk in people with higher numbers of melanocytic naevi. Oncogenes that prevent apoptosis have also been shown to play a role – BRAF mutations, among others, predispose an individual to the condition.
Clinically, diagnosis can be made through inspection with the naked eye alone – although dermoscopy may be a useful adjunct. Suspicious symptoms are any mole or pigmented lesion that is growing rapidly, changing shape or colour, itching, crusting or bleeding. Distinctive features of melanoma can be assessed using the ABCDE tool:
- A – Asymmetry
- B – (irregular) border
- C – colour variation
- D – Diameter >6 mm
- E – elevated surface
As well as in skin, it is possible for melanoma to present in mucosa with melanocytes, and it is not uncommon for melanomas to present under finger- or toenails.
Purely localised disease carries a good prognosis, and is treated with surgical excision – however this is insufficient if there is suspicion of metastasis, with a five-year survival rate of only 10%. Radiation has generally proved ineffective, so traditional treatment was limited to chemotherapeutics. This has been revolutionised in recent years, with the advent of biologic agents which target BRAF and other oncogene mutations greatly improving the treatment of melanoma in these patients.
Learn more at the Metastatic Melanoma Knowledge Centre.