ESR1 and breast cancer: The role of USP32 as a causal agent in breast cancer is further emphasized by a recent study that identified USP32–CCDC49 as one of the nine expressed fusion genes by structural analysis of the genome of ZR-75-30, an estrogen receptor-positive breast cancer cell line that has been used as a model system to study estrogen receptor-positive breast cancers that are insensitive to tamoxifen [36].