It has been known for a long time that there is a connection between dense breast tissue and an increased risk of developing breast cancer, but only recently have researchers begun to understand why.
Breast tissue is composed of several different types of cells which create different structures. There is the epithelium, consisting of duct cells and milk glands, the stroma, which is the connective tissue for the epithelial cells, and fat.
The 60 women who participated in the Mayo Clinic study were healthy with no history of breast cancer. Their breast tissue was biopsied to determine the difference in cellular composition between dense and non-dense tissue.
Results are now available from more than half of the participants who donated biopsy tissue. Dr. Ghosh found that areas of density contained much more epithelium (6 percent) and stroma (64 percent) and much less fat (30 percent), compared to non-dense tissue that contained less than 1 percent epithelium, about 20 percent stroma, and almost 80 percent fat. “This shows us that both the epithelium and stroma contribute to density, and suggests that the large difference in stroma content in dense breast tissue may play a significant role in breast cancer risk,” Dr. Ghosh says.
Another study took these results a step further:
In a second study, researchers also found that dense breast tissue has more aromatase enzyme than non-dense tissue. This is significant because aromatase helps convert androgen hormones into estrogen, and estrogen is important in breast cancer development, says that study’s lead investigator, Celine Vachon, Ph.D.
“If aromatase is differentially expressed in dense and non-dense breast tissue, this could provide one mechanism by which density may increase breast cancer risk,” Dr. Vachon says.
The researchers have found some strong links thus far, but they are recruiting more women for a second study to validate their findings.
“These are initial findings from one of the first attempts to study breast density at the level of healthy tissue. It doesn’t explain everything yet, but is providing really valuable insights,” says Dr. Ghosh, who established the patient resource for both studies.
Drs. Ghosh and Vachon are finishing their analysis of the initial 60 volunteers, and they are also enrolling more participants in order to validate and expand their findings. “No one knows why density increases breast cancer risk, but we are attempting to connect the dots,” Dr. Vachon says.
October is National Breast Cancer Awareness Month.
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