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. The gene discussed is ESR1; the disease is breast carcinoma.