Breast cancer is one of the most common cancers among women. While lifestyle and environmental factors play a role in developing the disease, genetics also contribute to risk. One area of interest is how breast tissue naturally changes as a woman ages. Inside the breast, tiny structures called terminal duct lobular units (TDLUs) are responsible for producing milk. These structures typically shrink and disappear over time in a process called TDLU involution. Women whose breasts retain more of these structures as they age may have a higher risk of developing breast cancer. Scientists don’t fully understand why, but they suspect that having more TDLUs means there are more cells in the first place that could potentially become cancerous.
To better understand why some women experience less TDLU shrinkage, researchers examined whether genetic factors play a role. Specifically, they looked at how a person’s overall genetic risk for breast cancer relates to the number of TDLUs in their breast tissue.
One way to measure genetic risk is through something called a polygenic risk score (PRS). This score is based on analyzing hundreds of common genetic variations, each of which contributes a small amount to a person’s likelihood of developing breast cancer. By adding up these small contributions, scientists can estimate a woman’s overall genetic predisposition to breast cancer.
This study explored whether women with a higher PRS—meaning they had more genetic risk factors for breast cancer—were more likely to retain their TDLUs, suggesting a slower process of shrinkage.
