ESR1 and breast cancer: A recent study described additional ESR1-e6 in-frame, inter-chromosomal translocation events involving the disabled homolog 2 gene, DAB2, and the glycogenin 1 gene, GYG1 (ESR1-e6>DAB2 and ESR1-e6>GYG1) producing stable in-frame ESR1 fusion proteins at metastatic sites in endocrine therapy refractory ER+ breast cancer patients.5 All of these ESR1-e6 fusions retain the N-terminus of ESR1 encoding the DNA binding and nuclear localization domains, suggesting some functionality.