ESR1 and cancer: AR-V7 presence is very common (51.5%) in breast tumor samples, especially in ERα- cancers and is correlated with higher levels of HER-2, other common occurrences of mutated AR include AR45 (25.0%), AR-V1, AR-V2 or AR-V4 (9.3%), AR-V3 (16.3%), AR-V9 (13.7%) and AR-V13, AR-V15 or AR-V18 (19.5%).