Researchers from 23andMe report in a BMC Medical Genetics paper published online in advance this week on their identification of seven SNPs that are significantly associated with breast size, two of which are in linkage disequilibrium with breast cancer-associated SNPs. Apart from those, one of the other seven SNPs is near, though not in linkage disequilibrium with, a SNP associated with breast cancer, the researchers report. In its paper, the 23andMe team says that the results of its genome-wide association study on self-reported bra cup size involving 16,175 women of European ancestry "provide insight into the genetic factors underlying normal breast development and show that some of these factors are shared with breast cancer." The authors add that though their results "do not directly support any possible epidemiological relationships between breast size and cancer," they could "contribute to a better understanding of the subtle interactions between breast morphology and breast cancer risk."
At its blog, The Spittoon, 23andMe says that "while the topic of breast size raised a few eyebrows when we first put out the survey … this paper demonstrates that important scientific insights can come from the most unlikely of places."