CYP19A1 and breast cancer: Using data from the Nurses' Health Study, Haiman et al [7] examined the relationship between the CYP19 tetranucleotide repeats and breast cancer risk among US Caucasian women; the authors found that harboring the 10 repeat allele [not identified in the Nordic population by Kristensen et al [5]] conferred a 3-fold increased risk of breast cancer (OR = 3.08, 95% CI 1.35–7.01).