Take a look at your right arm – got any moles? If so, how many?
That number could reveal how high your risk is for developing melanoma — one of the more dangerous types of skin cancer— according to an October 2015 study published in the British Journal of Dermatology.
After looking at the health data of more than 3,500 female Caucasian twins and then testing those findings on a control group of 415 men and women, researchers at King's College London found that the number of moles found on the right arm are the "most predictive" of the number of moles on the rest of the body.
Women with more than 11 moles on their right arms were nine times more likely to have 100-plus moles covering their entire bodies, which is a sign of a higher risk for melanoma.
But the Right Arm May Not Be Exactly, Well, Right
Before you rely solely on your right arm to predict the number of moles on the rest of your body, there are a few things to keep in mind.
"One, the study was done in England and part of the reason why they probably looked at the right arm is because it's the side that is exposed to the sun during driving — where in America, it's the left arm," says Misbah Khan, MD, clinical assistant professor of dermatology at NewYork-Presbyterian/Weill Cornell Medical Center.
Next, are you sure you know what a mole is in first place? A recent study found that almost 75 percent of melanoma patients didn't have the right tools (think full-length mirror or the help of someone else) or know-how to perform a full-body exam.
"The typical person tends to think of mole is a dark brown spot," Dr. Khan explains, but those spots may or may not be moles. "They can all very much look like brown dots, and to a person without a trained eye, it won't be possible for them to differentiate between a freckle and a mole."
She gives the example of a male patient whose arms were covered in freckles: "He had one highly abnormal mole on his left arm, which was 1 by 1.2 millimeter in size — that's how tiny it was! He didn't even know that it was right there on his wrist."
Finally, the arm is not typically the area of the body associated with problematic moles. "Women in general get more abnormal moles on their legs, while men in general get more moles on their backs," Khan says.
Other Skin Cancer Risk Factors to Remember
Certain people need to be more diligent than others, including Caucasians —"much more so if you have light or fair skin" — those who have developed moles throughout their lifetime as well as women experiencing hormonal fluctuations (e.g. due to birth control pills or pregnancy).
"When there is a hormonal shift, a woman is susceptible to developing pigment changes," Khan say. "That's why we take moles a little more seriously in women, especially during pregnancy, because it can accelerate the process of developing a mole and having it turn into melanoma."
The takeaway? "If you have actual moles on the arms, it's very important to go for a skin check at least once a year," Khan says. "And regardless of the number of moles you may — or may not — have, a physical exam for the skin is very important."