HealthDay News – The number of moles a female patient has on her skin may hint at her risk of developing breast cancer, according to two separate studies published in PLOS Medicine.

“While melanocytic nevi have been associated with genetic factors and childhood sun exposure, several observations also suggest a potential hormonal influence on nevi,” wrote Marina Kvaskoff, MPH, PhD, of the Centre for Research in Epidemiology and Population Health in Villejuif, France, and colleagues.

The researchers prospectively analyzed data from 89,902 French female patients aged 40 to 65 years in 1990. The number of nevi was collected at inclusion.

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From 1990 to 2008, 5,956 incident breast cancer cases (including 5,245 invasive tumors) were ascertained among the study participants. In models adjusted for age, education, and known breast cancer risk factors, women with “very many” nevi had a significantly higher breast cancer risk (hazard ratio, 1.13; 95% CI=1.01–1.27 versus “none”; P=0.04), although significance was lost after adjustment for personal history of benign breast disease or family history of breast cancer.

In a different study, Jiali Han, PhD, of the Indiana University Simon Cancer Center in Indianapolis, and colleagues, reported similar findings linking nevi to breast cancer incidence.

A total of 5,483 invasive breast cancer cases were diagnosed among 74,523 female patients who participated in the Nurses’ Health Study. Compared with female patients with no nevi, women with more cutaneous nevi had higher risks of breast cancer (HR, 1.04, 95% CI: 0.98–1.10 for 1–5 nevi; HR, 1.15, 95% CI: 1.00–1.31 for 6–14 nevi; and 1.35, 95% CI: 1.04–1.74 for 15 or more nevi; P=0.003 for all).

“Our results suggest that the number of cutaneous nevi may reflect plasma hormone levels and predict breast cancer risk independently of previously known factors,” concluded the researchers.


  1. Kvaskoff M et al. PLOS Medicine. 2014; doi: 10.1371/journal.pmed.1001660
  2. Han J et al. PLOS Medicine. 2014; doi: 10.1371/journal.pmed.1001659