Moles on arm can indicate higher skin cancer risk
19th October 2015 - Researchers at King's College London have found that having more than 11 moles on a person's arm can indicate they have a greater risk of developing melanoma, a type of skin cancer that can be fatal.
They say their findings could help GPs establish a person's risk of skin cancer.
Every year in the UK about 13,300 new cases of melanoma are diagnosed, with more than 25% of cases in people under 50, and there are about 2,000 deaths. Establishing a person's risk can help them to take steps to prevent getting skin cancer and to also be aware of the symptoms. If caught early, melanoma can be treated.
Moles and melanoma
There are certain characteristics that puts a person at a higher risk of developing melanoma, such as having pale skin that burns easily, having red or blonde hair, and having a lot of moles. In fact, the more moles you have on your body, the greater your chances of developing melanoma - each mole increases a person's risk factor by 2-4%.
In the study, published in the British Journal of Dermatology, the researchers say that total body naevus count (TBNC) - naevus is another name for mole - is one of the most important factors for determining the risk of melanoma. However, although a naevus count is an important indicator of a person's risk factor, doing a total body examination is time consuming and rarely practised by GPs.
The aim of the study, funded by the Wellcome Trust, was to identify a site on the body that could be used as a 'proxy' for a full body mole count and to establish the cut off number of moles that can be used to predict a person's risk of developing melanoma.
Previous small-scale studies have found the arm to be the best site for predicting a TBNC. For this study researchers used a much larger sample of participants, with data collected from 3,694 healthy female Caucasian twins between January 1995 and December 2003 - however, 840 women were excluded because of missing data on skin type. Trained nurses counted moles in 17 different sites on each particpant's body.
The researchers found that compared to women with fewer moles, women with more than 7 moles on their right arm had nine times a greater likelihood of having more than 50 moles in a TBNC, and women with more than 11 moles had nine times a greater chance of having more than 100 moles in a TBNC than in those with fewer than 11 moles. The study also showed that the area above the right elbow was a particularly good indicator for a total body mole count, and legs were also a strong indicator. Analyses found that these findings were the same whether the comparison was made between twins or unrelated women. The study's findings were replicated in a further study that involved 415 participants, both men and women. In their conclusion, the researchers say that an arm count of more than 11 moles is "associated with a significant risk of having more than 100 naevi" and indicated that doing a mole count on an arm would make it possible for a quick clinical evaluation of melanoma risk in general practices.