Stratified Fisher’s exact tests confirmed that the lower mutation frequencies in TA-UC (PIK3CA, combined P = 0.008; PIK3R1, combined P = 0.001) were not driven by the different distributions of tumor grades in our TA-UC and de novo UC cohorts (Supplementary Note 3 and Supplementary Fig. 1a). This evidence concerns the gene PIK3R1 and neoplasm.