Mammographic density is one of the strongest predictors of breast cancer risk. The mechanism by which breast density increases breast cancer risk is unclear although it has been hypothesized that breast density reflects cumulative exposure to estrogens.
Channing Laboratory, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, 181 Longwood Avenue, Boston, MA 02115, USA. rulla.tamimi@channing.harvard.edu
