In two separate studies, American and French scientists found that the more moles a woman had, the greater her average risk of breast cancer. In one study, led by Jiali Han, PhD, of the Indiana University Simon Cancer Center in Indianapolis, women with ≥15 moles on a single arm were 35% more likely to develop breast cancer than women with no moles.
The findings were similar in the second study, which followed nearly 90,000 French women aged 40–65. However, moles were linked to an increased risk only among women who developed breast cancer before menopause.
While the connection between moles and breast cancer is not obvious, experts pointed to one plausible explanation: estrogen. “They could be a marker of lifetime exposure to estrogen,” Barbara Fuhrman, PhD, an assistant professor at the University of Arkansas for Medical Sciences in Little Rock, told HealthDay. But there could be other underlying reasons for the association – even some kind of genetic factor, said Fuhrman, who wrote an editorial published June 10 with the studies in the online journal PLOS Medicine.