Moles and Breast Cancer

Date: 06/28/2014    Written by: Beth Levine

Moles and Breast Cancer

If you are a woman with a lot of moles, chances are you're aware that you may have an increased risk of developing skin cancer. However, you may not be aware that those moles may be an indicator of elevated risk for breast cancer as well, according to new research.

The study, which took place at the Indiana University Simon Cancer Center in Indianapolis, discovered that the presence of a greater number of moles on a woman's skin appears to correspond with having an increased risk of developing breast cancer.1 The subjects were more than 74,000 American women who were participating in the Nurses' Health Study. The research began in 1986, when this group of volunteers was between the ages of 40 and 65. Toward the beginning of the trial, they were instructed to examine their left arm and tally the total number of moles they found.

Fast forward 24 years, when the researchers analyzed the information and determined that close to 5,500 of the subjects had developed breast cancer at some point along the way. When they cross-referenced those with a breast cancer diagnosis with the mole count information, a pattern became visible. The data showed the risk of breast cancer increased correspondingly with the quantity of moles a subject had. Women without moles were by no means safe from breast cancer, as 8.5 percent of them were eventually diagnosed with the disease. However, of those with between one and 14 moles, the breast cancer rate was nearly 10 percent. And even worse, in the women who had 15 or more moles on an arm, the number went up to 11.4 percent. While that may not seem like an enormous difference, a variation of nearly three percent in a group of 74,000 equals more than 2,000 extra cases of breast cancer.

Even after controlling for a number of factors that could potentially influence the outcome--such as age, skin tone, ultraviolet exposure, and lifestyle--the results did not change. The participants with greater numbers of moles were determined to have a 35 percent increased chance of being diagnosed with breast cancer as compared to their peers with no moles.

And the findings were bolstered by a second, completely separate, study that was conducted at the National Institute of Health and Medical Research in Paris, France. This trial was even larger, including 89,902 subjects, all of who were women between the ages of 40 and 65 residing in France. These scientists also determined that a greater number of moles on a woman's skin is related to a higher risk of breast cancer. However, in this case, the association only held true for the participants who suffered from breast cancer prior to going through menopause.2

Why would moles possibly have anything to do with breast cancer? The researchers involved in the U.S. study theorize that it has to do with the influence of estrogen. They measured the hormone levels in blood samples taken from a portion of the women who were postmenopausal close to the start of the investigation, and discovered that those with more moles had higher levels of estrogen and testosterone on average.

We know that greater exposure to estrogen over time is linked to breast cancer. But there may also be a less understood association between estrogen and moles. We do know that hormones affect moles, which has long been noted in such instances as the darkening of moles during pregnancy. And in the study, it was mainly hormone-receptor positive breast cancer, which is stimulated by estrogen, that was found in the participants with more moles.

So, if you are a woman with an abundance of moles, it probably couldn't hurt to be a little extra vigilant about performing monthly breast self-exams and scheduling those mammograms. Another way to help safeguard your health might be taking steps to balance out those hormones and rid yourself of excess estrogen. There are many factors that can increase the levels of estrogen in your body, including some you have control over such as being overweight. Starting to exercise regularly and eating a nutritious, low calorie diet can also offer some natural health protection.

  • 1. Norton, Amy. "Moles may be sign of higher breast cancer risk." CBS News. 11 June 2014. Accessed 19 June 2014.
  • 2. Kvaskoff, Marina; et al. "Association between Melanocytic Nevi and Risk of Breast Diseases: The French E3N Prospective Cohort." PLOS Medicine. 10 June 2014. Accessed 20 June 2014.

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