Sung H, et al. - Researchers examined how terminal duct lobular unit (TDLU) measures are related to mammographic density (MD) among Chinese women, a low-risk population for breast cancer but with a high prevalence of dense breasts. Using the Breast Imaging Reporting and Data System (BI-RADS) density classification, they scored 144 diagnostic pre-treatment digital mammograms from breast cancer cases at a tertiary hospital in Beijing. Dense breasts were evident in 63% of women ≥50 years. Compared to cases with non-dense breasts (BI-RADS, a-b), those with dense breasts had greater TDLU count, longer span, and greater acini count. Dense breasts were noted in 91% of women <50 years. In line with previous reports, this study identified the associations between extensive MD and reduced TDLU involution, supporting the premise that breast cancer risk linked with extensive MD may be connected to the amount of “at-risk” epithelium.