Density, and Subsequent Risk of Breast Cancer

Mammographic density is one of the strongest predictors of breast cancer risk ( 1). The radiographic appearance of the breast on a mammogram depends on the composition of the breast. Areas of fat are radiolucent and appear dark on the fi lm of a screening mammogram, whereas areas of epithelial cells and connective tis-sue are radiodense and appear light on a mammogram (i.e., they are considered to be “mammographically dense”). Women whose breasts contain at least 75 % dense tissue are at a four- to sixfold greater risk of breast cancer than women with entirely fatty breasts (i.e., no measurable dense tissue) ( 1, 2). The biologic mechanism by which mammographic density is associated with breast cancer risk is unclear. Epidemiologic data ( 3, 4) support the association between endogenous sex steroids and the risk of breast cancer in postmenopausal women in the general population, although it is unclear whether this association als