In particular, AR is present in approximately 70% to 90% of invasive breast carcinomas, a percentage equal to or higher than that of ER (70% to 80%) and its expression shows significant association with favorable clinicopathological characteristics, such as lower tumor grade, smaller tumor size, better outcomes and improved response to hormone therapy in ER-positive breast cancers [14-18]. The gene discussed is ESR1; the disease is invasive breast carcinoma.