(RxWiki News) The amount of sex hormone's in a woman's blood may play a role her risk of breast cancer. And those sex hormone levels may show themselves in more obvious ways than once thought — in the form of moles on the skin.
Two recent studies found that women with high numbers of cutaneous nevi, more commonly known as moles, were at increased risk for breast cancer.
The researchers believe that the number of moles a woman has could be used as a marker of her breast cancer risk.
"Ask your doctor about breast cancer screening guidelines."
The first of these two studies was led by Jiali Han, PhD, of Brigham and Women's Hospital and Harvard Medical School.
This study included 74,523 women from the Nurses’ Health Study (NHS), which was conducted in the United States from 1986 to 2010. These nurses were an average age of 52 years old.
Dr. Han and team asked the participants in the NHS to report the number of moles on their left arm that were bigger than 3 millimeters in diameter at the initial assessment.
These researchers found that compared to the nurses who had no moles, those with one to five moles were 4 percent more likely to be diagnosed with breast cancer. The nurses with six to 14 moles were 15 percent more likely to be diagnosed with breast cancer, and those with 15 or more moles were 35 percent more likely to be diagnosed with breast cancer.
The researchers determined that nurses with no moles had an absolute lifetime risk of 8.48 percent for breast cancer. This number increased to 8.82 percent for the nurses with one to five moles, to 9.75 percent for the nurses with six to 14 moles and to 11.40 percent for the nurses with 15 or more moles.
Another analysis on a smaller group of women showed that the postmenopausal nurses with six or more moles had higher levels of estrogen and testosterone (sex hormones) in their blood compared to the postmenopausal nurses with no moles. The association between moles and breast cancer risk in these postmenopausal nurses was no longer significant after adjusting for increased hormone levels.
The lead author of the second study was Marina Kvaskoff, MPH, PhD, from the French National Institute for Health and Medical Research and Harvard Medical School.
This study included 89,902 women from E3N, a cohort of French women between the ages of 40 and 65 years old in 1990.
Dr. Kvaskoff and colleagues asked the participants to report whether they had no moles, a few moles, many moles or very many moles.
The findings showed that the women with “very many” moles were 13 percent more likely to be diagnosed with breast cancer than the women with no moles.
Dr. Kvaskoff and team determined that this link between moles and breast cancer risk was no longer significant after adjusting for known breast cancer risk factors, such as history of non-cancerous tumors in a breast and family history of breast cancer.
These researchers did find, however, that the number of moles associated with these known breast cancer risk factors. In other words, women with higher numbers of moles were more likely to have a history of non-cancerous breast tumors or a family history of breast cancer.
The authors of both studies concluded that their findings did not show that moles caused breast cancer. Rather, the findings showed that moles may be affected by levels of sex hormones. The researchers believe that sex hormones may play a part in the development of breast cancer.
Both of these studies suggest that the number of moles might be used to determine a woman’s risk of breast cancer. However, the researchers were still unsure how exactly this factor would improve doctors' ability to estimate breast cancer risk.
More research is needed on the specifics of how moles may help to predict breast cancer.
Both of these studies had similar limitations — the data were based on self-report, and the majority of the participants were white.
These studies were published on June 10 in PLOS Medicine.
The National Institutes of Health funded the Nurses’ Health Study. The Mutuelle Generale de l’Education Nationale, the European Community, the French League against Cancer, Gustave Roussy and the French National Institutes for Health and Medical Research provided funding for the study by Dr. Kvaskoff and colleagues.