How to gauge skin cancer risk: count the moles on your arm

According to research carried out at King’s College London, the number of moles on the body is a reliable indicator of skin cancer risk — and academics have developed a new way of counting them.

The researchers say that their investigation has revealed that by counting the number of moles found on a ‘proxy’ area of the body (an arm, for example) GPs are able to determine the number of moles on the entire body.

Although just 20 to 40 per cent of melanoma cases originate in pre-existing moles, mole count is one of the most reliable indicators of skin cancer risk. The researchers say that the difficulty of counting moles across the entire body is ‘time-consuming in a primary care setting’, but that this method is much easier. This is important because with each mole the risk of melanoma is thought to increase by between two and four per cent.

This study, funded by the Wellcome Trust, used data from 3,594 female Caucasian twins to identify the most useful proxy site for a full-body mole count. The twins were given a skin examination that recorded the number of freckles and moles on 17 body sites.

This survey was then replicated in a wider sample of volunteers from a UK melanoma case control study. The researchers found that the right arm was the most reliable proxy site. They found that women with more than seven moles on their right arm had nine times the risk of having more than 50 moles on the whole body and those with more than 11 on their right arm were more likely to have over 100 on their body in total, meaning they were at a higher risk of developing a melanoma.

The researchers say their findings could help GPs to more easily identify those at the highest risk of developing skin cancer.