Aromatase is also highly expressed in breast cancer producing higher levels of estrogen.15 However, breast cancer cells constantly develop resistance to aromatase inhibitors by acquiring estrogen receptor mutations, truncation and upregulation of ER-related transcription factors activator protein 1 (AP1) and NF-κB, aromatase inhibitors are effective in breast cancer treatment.16–18. This evidence concerns the gene CYP19A1 and breast cancer.