Specific forms of ΔCCDC170 leads to reduced tamoxifen sensitivity in experimental models.2 Recently, an additional ESR1-e2 fusion with the acidic residue methyltransferase 1 gene, C6orf211 (ESR1-e2>C6orf211) fusion as well as ESR1-e2>CCDC170 fusions have been identified in AI resistant breast tumors, but more studies are required to test whether these ESR1-e2 fusions produce pathogenic proteins.3 Taken together, these ESR1 fusion events have the potential to generate pathogenic, truncated forms of fusion partner proteins, but does not produce ESR1 fusion proteins (Figure 1B). This evidence concerns the gene CCDC170 and breast neoplasm.