CYP19A1 and breast cancer: The occurrence and severity of breast adipose tissue inflammation is higher in obese compared to normal weight women34 and in postmenopausal relative to premenopausal women.35,36 Breast adipose tissue inflammation is associated with elevated aromatase levels, the rate-limiting enzyme in estrogen biosynthesis,37 and similar inflammation has been noted at distant sites.38,39 Thus increased estrogen production arising from aromatase activity, particularly in the postmenopausal environment, may selectively drive proliferation in estrogen-dependent breast cancer.