Mammographic density: a heritable risk factor for breast cancer.

Abstract

The appearance of the breast on mammography varies among women, reflecting variations in tissue composition. Stroma and epithelium attenuate x-rays more than fat and appear light on a mammogram, which we refer to here as " mammographic density, " while fat appears dark. We show evidence that mammographic density is a strong risk factor for breast cancer, and that risk of breast cancer is four to five times greater in women with density in more than 75% of the breast, compared with those with little or no density. Density in more than 50% of the breast may account for a large proportion of breast cancers. Density is influenced by age, parity, body mass index, and menopause but these factors a..