Whole genome and whole exome analyses of tumors have been the primary means to establish the ultrahypermutated (>100 Mutations per megabase) unique mutational signature that distinguish Pol ε tumors from other cancers (Alexandrov et al., 2013a; Alexandrov and Stratton, 2014; Shinbrot et al., 2014; Shlien et al., 2015; Alexandrov et al., 2013b; Campbell et al., 2017). This evidence concerns the gene EPX and cancer.