Quick! Count the Moles on Your Arm

Melanoma risk could be reflected in number of moles on your right arm


Have more than 11 moles on your right arm? You could have a higher-than-average risk of melanoma.

That's what the researchers behind a recent study published in the British Journal of Dermatology are saying, anyway.

If your arm is covered in moles, don't panic — these researchers are just talking about melanoma risk. A high risk doesn't necessarily mean a sure thing. Still, you may want to talk to your dermatologist.

But what's so special about the moles on your right arm? Nothing, really. The King's College London researchers behind this new study found that the right arm could be used as a "proxy" area to determine the likely number of moles on the rest of the body — giving doctors a quicker way to assess your risk of melanoma, a potentially deadly form of skin cancer.

"This study follows on from previous work to identify the best proxy site for measuring the number of moles on the body as a whole," said lead study author Simone Ribero, of King's College's Department of Twin Research and Genetic Epidemiology, in a press release. "The difference here is that it has been done on a much larger scale in a healthy Caucasian population without any selection bias and subsequently replicated in a case control study from a similar healthy UK population, making the results more useful and relevant for [doctors]."

See, doctors have thought for a while that the number of moles on the body is one of the biggest risk predictors for melanoma. But counting the number of moles on the entire body is often too difficult to do, especially for every patient. A quick count of the moles on the right arm — along with some fairly simple multiplication — could provide a quick snapshot of your melanoma risk, though.

Say you find out you've got a high risk of melanoma — what does that mean for you? Well, it could mean you need cancer screening more often than average — but that's something for you and your doctor to decide. Still, knowing your risk can up your chance of survival. According to a 2014 article in JAMA, "The goal of screening is to catch cancers early. Early-stage cancers are easier to treat than later-stage cancers, and the chance of survival is higher."

Dr. Ribero and team noted that past studies had identified areas of the body that could be used as proxy sites for counting moles, but these studies were much smaller than the current one. Dr. Ribero and team looked at data from nearly 3,600 white, female twins. Later, they repeated their study in a broader sample that also included men.

In both study groups, a higher mole count on the right arm predicted the number on the whole body. Women in this study with more than 11 moles on their right arm were likely to have more than 100 moles total. Considering that some experts think each mole on the body raises the average melanoma risk by between 2 and 4 percent, 100 moles starts to sound like a pretty high risk.

Again, though, don't panic — just talk to your doctor. According to the American Cancer Society, the 10-year survival rate (meaning patients lived at least 10 years after diagnosis) for stage I melanomas ranges from 86 to 95 percent.