(Ivanhoe Newswire) -- Scientist report they have found a the location of a gene associated with dense breast tissue, a factor known to increase a woman's risk of developing breast cancer.

Finding these genes means researchers may have a new lead on how to develop ways to reduce breast tissue density and, possibly, breast cancer risk.

Researchers from the Mayo Clinic and H. Lee Moffitt Cancer Centers studied the DNA of nearly 900 people. They report a region on chromosome 5p is significantly associated with dense breast tissue. The region contains 45 genes, and one or more of these genes could determine, in part, how dense a woman's breast tissue is.

Women with dense breasts have a higher proportion of stromal and epithelial tissues to fat than women with less dense breasts. Stromal and epithelial tissues can mask tumors in mammograms because both types of structures show up as white in the images, but this is only part of the problem. Age, diagnosis of abnormal cells on a breast biopsy, and inheritance of rare gene mutations, like BRCA1 and BRCA2, are the only risk predictors of breast cancer stronger than breast density. Women with dense breasts are three- to five-times more likely to develop breast cancer than women with less breast density.

"At this point, we have not identified a gene or genes for breast density but a promising location to investigate further," Celine Vachon, Ph.D., an epidemiologist at the Mayo Clinic in Rochester, Minn., was quoted as saying. "Identification of genes for breast density will improve our understanding of how breast density influences breast cancer development in women."

SOURCE: Cancer Research, 2007;67:8412–8418