Mammographic Density: Effects on Breast Cancer Detection and Risk

Fatty breast tissue is radiographically lucent and appears dark in mammograms. By contrast, stroma and epithelium are radiographically dense and appear light, making mammograms more challenging to read. Investigators in Canada analyzed data from three case-control studies (1112 case-control pairs; mean age at screening, 57) that included screening mammograms and follow-up to assess the association between mammographic density at the time of screening and risk for breast cancer. Each image was assigned to one of six categories, based on percentage of density. Cases of breast cancer were diagnosed from 1981 through 1999.

Compared with women who had radiographic density in <10% of their mammograms, those who had density in ≥75% had an elevated …