What is the Molecular Basis of Breast Density?

Molecular Basis of Breast Density

Little is known about the exact cause of many breast cancers. We do know that women, described as having high breast density (whiteness on the mammogram), have a 4-6-fold increase in breast cancer risk. This is compared to women of the same age, described as having low breast density. Breast density is one of the strongest predictors of whether a woman will develop breast cancer in the future.

Breast density is not a measure of how the breasts feel but describes how the breasts absorb X-rays and therefore look on a mammogram. On the whole, fatty breasts have low overall density – fat appears black or grey on the mammogram. Breasts containing a lot of connective tissue (which act as a scaffold for breast cells) have high density. Emerging evidence shows that there are changes within the connective tissue (which is rich in collagen) in women with high breast density. This in turn promotes cancerous changes within the breast cells.

The nature of these changes within the connective tissue, and how these changes subsequently promote breast cancer, is not well understood. Our early experiments suggest that the organisation of collagen proteins within breast tissue may be very important. We wish to study this further and in greater detail. It could eventually help us provide more targeted breast screening, the early, accurate, diagnosis of breast cancer, and possibly lead to improved approaches for prevention.

To fill this important gap in our knowledge, we will determine differences in tissue composition, structure, stiffness, and expression of genes in high and low breast density tissue. And of early breast tumours arising in the same individuals. To do this we will recruit patients undergoing mastectomy for breast cancer.

We will study breast tissue removed as part of the cancer operation, comparing normal breast tissue to cancer tissue in women with high breast density and also in women with low breast density.