ESR1 and breast cancer: A systematic screen was conducted to identify ESR1 translocations in three datasets: 728 primary breast tumors from The Cancer Genome Atlas (TCGA) (Ciriello et al., 2015), 81 primary breast cancers from two neoadjuvant aromatase inhibitor (AI) clinical trials (Ellis et al., 2011; Olson et al., 2009), and 25 biopsy samples from patients with late-stage ER+ breast cancer (Figure 1A).