ESR1 and breast cancer: In this study, we explored the occurrence of fusion transcripts of three of the most commonly reported fusion partners of ESR1 (i.e. CCDC170, AKAP12 and ARMT1) and determined the associations of their presence with clinical outcome in a cohort of 732 breast cancer patients allowing us to investigate their predictive value for endocrine treatment failure as well as their prognostic value.