More recently, aromatase inhibitors (AIs) were shown to further reduce the risk of recurrence or death from BC as compared with tamoxifen in post-menopausal women (Crivellari et al, 2008; Forbes et al, 2008) and constitute an alternative option now recommended for the adjuvant treatment of early BC (National Institute for Health and Clinical Excellence, 2006; Goldhirsch et al, 2009; Burstein et al, 2010). Here, CYP19A1 is linked to breast cancer.