Researchers in this study wanted to understand whether genetic ancestry is related to differences in normal breast tissue, and how those differences might influence breast cancer risk. One important feature they focused on is terminal duct lobular unit (TDLU) involution, which is the natural shrinking of breast structures as women age. Women with less involution—meaning more remaining glandular structures—are known to have a higher risk of developing breast cancer.
To investigate this, the researchers analyzed normal breast tissue samples from women with diverse genetic backgrounds. They used genetic data to estimate each woman’s ancestry and then measured detailed features of breast tissue, including the number and size of TDLUs and how much involution had occurred.
They found that women with a higher proportion of African ancestry tended to have less TDLU involution, meaning more glandular tissue remained in the breast. These differences were not explained by age, reproductive history, or other common risk factors.
Overall, the findings suggest that differences in normal breast tissue structure—linked to genetic ancestry—may help explain variations in breast cancer risk across populations.
