Number of Moles on One Arm Could Predict Melanoma Risk

The number of moles present on one arm could be a useful tool in assessing a person’s risk for melanoma in the primary care setting, a new study has found.

The study, published in the British Journal of Dermatology, was designed to identify a smaller proxy area of the body that could be used to accurately estimate the number of nevi on the body as a whole.

“The findings could have a significant impact for primary care, allowing general practitioners to more accurately estimate the total number of moles in a patient extremely quickly via an easily accessible body part,” said study researcher Simone Ribero, MD, PhD, of King’s College London, United Kingdom, in a prepared release. “This would mean that more patients at risk of melanoma can be identified and monitored.”

According to the study, total body nevi count is among the most important predictive tools for a person’s melanoma risk. In this study, Ribero and colleagues assessed 17 body sites to determine their predictive value for estimating total body nevi count. They used data from a study of 3,694 female twins who underwent nevi counting as part of a larger study. Nevi were defined as a melanocytic lesion 2 mm or greater in diameter.

The researchers found that the most predictive sites were the arms and legs, with adjusted correlation coefficients of 0.50 for the right arm and 0.51 for the left arm (P < .001 for both) and 0.49 and 0.48 for the right and left legs, respectively (P < .001 for both).

The researchers then replicated their study in a control group of 415 healthy patients taken from a melanoma case-control study. In this study, the arm remained the most predictive body site for total body nevi count in both men and women.

“No differences were observed between males and females in the replication study, so gender is unlikely to have had a major effect on the selection of the best site for predicting total body nevi count,” the researchers wrote.

In the cohort of twins, the women with more than 11 nevi on their right arm had a ninefold increased likelihood of having more than 100 nevi on their body compared with women with less than 11 nevi (odds ratio [OR], 9.38 [95% confidence interval (CI), 6.71–13.11]).

“Clinically, Caucasian populations tend to have more nevi on the upper arm compared to the lower arm and we report a different prediction for arm above compared to below elbow,” the researchers wrote. “The lower arm alone is a more difficult site as this site is more likely to include lentigines, which could be miscounted for nevi.”

Looking specifically at the right arm above the elbow, the researchers found that women with more than 8 nevi had a greater than ninefold risk for having a total body nevi count of more than 100 (OR, 9.83 [95% CI, 7.10–13.60]).

“Although legs were also predictive of total body nevi count, the arm yielded the highest correlations and for clinical practice will be a more accessible site,” the researchers wrote. “Being able to estimate total body nevi count by quickly counting nevi on one arm could be a very useful tool in predicting melanoma risk in healthy populations.”