Wednesday June 11, 2014 (foodconsumer.org) -- A woman may have some idea about her risk of breast cancer simply by counting moles equal or greater than 3 mm in diameter on her left arm.  Quite a few studies suggest that women with a high number of moles are at high risk of breast cancer.

In this week's issue of PLOS Medicine, two studies authored by Jiali Han and colleagues and Marina Kvaskoff and colleagues show a link between the number of melanocytic nevi and breast cancer risk among middle-aged women.

Melanocytic nevi, also known as moles, are benign tumors of the skin, which are commonly developed in childhood and adolescence and which may disappear late in life.

Early studies have associated moles with increased risk for malignant melanoma.  But now studies also link the number of moles to the risk of breast cancer.

Data used in the study led by Han and colleagues came from the Nurses' Health Study (NHS) cohort of 74,523 white women aged 40 to 65 in 1986 in the United States.  Participants were asked to count and report the number of moles with equal or greater than 3 mm in diameter on their left arms, from shoulder to wrist.  All participants were followed through 2010.

The study reveals that women with 15 or more moles were 35% more likely than those without any moles to be diagnosed with breast cancer.

In another study, Kvaskoff and colleagues analyzed data from the E3N Teachers' Study Cohort of 89,902 women aged 39 to 66 in France who were enrolled in the study between 1989 and 1991.   Participants were asked to count and report their numbers of moles and were followed through 2008.

The study shows that women reporting the most moles were at 13% higher risk of breast cancer, compared with those without moles.  After adjustment for other confounders, the risk was 8% higher among those with the most moles.

Kvaskoff and colleagues found the association between the number of moles and risk of breast cancer depending upon the menopausal status, that is, in premenopausal women, those with very many moles were 34% more likely to develop breast cancer, compared with those who reported none.  But no association was observed among postmenopausal women.

In contrast, Han and colleagues did not find the association depending upon the menopausal status.

It should be noted that the two cohorts were different and it can't be that everything in the two cohorts was the same!!

Barbara Fuhrman and Victor Cardenas in a commentary suggest that moles are hardly the cause for the increase in the risk of breast cancer because moles and breast cancer have "distinct origins and locations."  High number of moles and high risk of breast cancer may share the same cause though, the authors suggest.

Sex hormones can be the shared cause.  Exposure to high sex hormones is linked with both high numbers of moles and high risk of breast cancer.  It has been observed that estrogen promotes that the development of breast cancer while a high number of moles are likely to be acquired during puberty and the appearance and size of moles are changed during pregnancy.  (David Liu, PHD)

References

Mingfeng Zhang, Xuehong Zhang, Abrar A. Qureshi, A. Heather Eliassen, Susan E. Hankinson, Jiali Han (2014) Association between Cutaneous Nevi and Breast Cancer in the Nurses' Health Study: A Prospective Cohort Study. PLoS Med 11(6): e1001659. doi:10.1371/journal.pmed.1001659

Marina Kvaskoff , Anne Bijon, Sylvie Mesrine, Alice Vilier, Laura Baglietto, Agnès Fournier, Françoise Clavel-Chapelon, Laure Dossus, Marie-Christine Boutron-Ruault (2014) Association between Melanocytic Nevi and Risk of Breast Diseases: The French E3N Prospective Cohort. PLoS Med 11(6): e1001660. doi:10.1371/journal.pmed.1001660

Fuhrman B, Cardenas V (2014) Melanocytic Nevi as Biomarkers of Breast Cancer Risk. PLoS Med 11(6): e1001661. doi:10.1371/journal.pmed.1001661