Aromatase plays a crucial role in the final stage of estrogen biosynthesis, and can be affected by genetic factors resulting in the changes in serum sex hormone levels [7, 8], and recent evidences indicated that the rs4646 variant of CYP19A1 might be a predictive factor of the benefit of aromatase inhibitor treatment for breast cancer [9]. Here, CYP19A1 is linked to breast cancer.