Research published in the British Journal of Dermatology found a surprisingly correlation in the number of moles on that one particular appendage and the instance of melanoma, which is the deadliest type of skin cancer.
Doctors have known for a long time that counting moles could go a long way in determining risk factors, but counting all of them on an entire body can be pretty time consuming and make people uncomfortable. So scientists wanted to figure out a better way, maybe by focusing on a particular area.
At first, researchers studied 3,594 twins in their Twins UK study group and counted moles in 17 different body areas. The participants were all female and white in that first glance, but the scientists expanded the study group to look at a more diverse population, and they found the same thing in each case.
It turns out that the right arm is the best predictor of skin cancer. People with more than seven moles on that arm have a nine times likelier chance of having more than 50 moles over their body. Those who have more than 11 on their right arm are likely to have more than 100 over their body.
So, with a 2 to 4 percent increase in the risk for skin cancer for every mole you have on your body, your right arm could be the guide to whether or not you should really investigate elsewhere.
“This would mean that more patients at risk of melanoma can be identified and monitored,” Simone Ribero of the Department of Twin Research & Genetic Epidemiology said in a statement, adding that it could give doctors a better guide to evaluating patients.
Between January 1995 and December 2003, the participants underwent a skin examination in which researchers recorded their skin type, eye color and freckles, hair color and moles.
The researchers also confirmed the link they found between total mole count and the number of moles on the right arm using data from another study, which included male and female participants.
Two other body sites — the area above the right elbow, and the legs — were also found to be particularly predictive of a person’s total body mole count. In men, the number of moles on the back was a good indicator of total mole count as well, the researchers said.
By the way, the study found a few other areas where a concentration of moles could be an indicator, including the area above the right elbow and on people’s legs. In men, you could look on the back.
However, there are other factors that may better determine a person’s risk of melanoma, said Dr. Hooman Khorasani, chief of dermatologic and cosmetic surgery at Mount Sinai Hospital in New York, who was not involved in the study.
“Genetic composition is way more important, as well as how the moles look,” Khorasani said. For example, moles that doctors call “dysplastic nevi,” which are unusual, benign moles butthat resemble moles that indicate the presence of melanoma are essential to distinguish from other moles because they signal an increased cancer risk.
According to the American Cancer Society, people with greater exposure to ultraviolet (UV) light, and those with fair skin, freckles, light hair or a family history of melanoma face an increased risk of melanoma.
“It’s more important that you look at a person’s risk factors than count the number of moles on their arm,” Khorasani said.
If you are especially concerned, you can download the new Mole Mapper app, which was recently released by Oregon Health & Science University and is part of Apple’s ResearchKit. The app helps you track the growth or shape of moles over time so you can know if they have changed, which could be an indication of cancer.