Connecting the dots: breast tissue density and breast cancer

Does dense breast tissues increase your risk for breast cancer? Research studies done by Mayo Clinic researchers can now give some answers about the link between breast density and breast cancer risk. The first research showed that dense breast tissues contain more cells that may promote breast cancer while the second research showed that dense breast tissues contain more aromatase enzyme than non-dense ones. This aromatase enzyme is reported to help convert androgen hormones into estrogen which is involved in breast cancer development.

Mayo clinic researchers took 8 core-needle biopsies from the breast of 60 women volunteers, age 40 to 85. All volunteers have no history of breast cancer. These research studies were unique since previous studies have focused only on dense tissues taken from women with breast diseases.

In the first study, Dr. Karthik Gosh, M.D., a Mayo clinic breast cancer researcher and her team, determined the percentage of epithelium, stroma and fat tissues from the biopsy samples collected. The epithelium tissues are composed of milk ducts and ductal cells while stroma is the tissue that supports the epithelial cells.

Analyses of more than half of the samples showed that dense tissues contain more epithelium (6%) and stroma (64%) and less fat tissues (30%). Non-dense tissues, on the other hand, contains more fat (almost 80%), and lesser epithelium (1%) and stroma (20%) tissues. “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.

In the second study, Dr. Celine Vachon, ead investigator of the study and her colleagues examined the dense and non-dense tissue samples for the presence of aromatase. The result showed that aromatase enzyme was higher in the stromal cells of dense tissues compared to non-dense ones. They say that these findings can help explain why women with denser breast have higher risk of breast cancer than women with less dense breasts.

“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.

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.

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