The increased genome copy numbers of both loci in this case, together with the location of these two genes neighboring CCDC170 on chromosome 6q25, suggest that this fusion was generated by tandem duplication of the ARMT1-CCDC170-ESR1 locus, as identified in breast cancers bearing the recurrent ESR1-CCDC170 fusion [31]. Here, CCDC170 is linked to breast cancer.