Roll up your sleeves and get counting: Tallying the number of moles on your arm can help predict your chances of melanoma, researchers from King’s College London discovered.
In the study, people with 12-plus moles on one of their arms were more than 9 times more likely to have over 100 moles throughout their entire body—a known risk factor for the deadly skin cancer melanoma—than those with fewer spots on their arms.
And looking at the upper arm in particular was even more predictive. People with 8-plus moles above their elbows were nearly 10 times more likely to have more than 100 moles throughout their body.
Having an accurate proxy to determine total-body mole count is important because an excess of moles spikes your risk of developing melanoma, says study author Veronique Bataille, M.D., Ph.D.
In fact, a previous Italian meta-analysis of 46 studies concluded that people with 100-plus moles have more than six times the risk of melanoma as those with 15 or fewer lesions. That may be because the same genetic factors that spur mole production may also be behind melanoma development.
Plus, 20 to 40 percent of all melanomas arise in pre-existing moles. And if these moles are subjected to UV exposure—say, if you’re out in the sun without SPF—they can develop mutations that can jumpstart the melanoma process, says Adnan Nasir, M.D., the Men’s Health dermatology advisor.
Just make sure you’re not ID’ing freckles as moles. The latter tend to be larger than 2 millimeters (the diameter of the point on a crayon), with a darker brown color and a well-defined border. Freckles tend to be smaller and lighter brown, occur in multiples—especially in redheads or blondes—and have less defined edges, says Dr. Bataille.
If your count comes up high, your next step is to head to the doctor so a pro can take a look and screen for any high-risk lesions, says study coauthor Simone Ribero, M.D, Ph.D. Early detection of any possible melanomas can boost your chances of beating it.