PIK3CA mutations activate the PI3K-PTEN-AKT pathway which is downstream from both the EGFR and the RAS-RAF-MAPK pathways.The somatic mutations found thus far in PIK3CA are oncogenic, and the majority of them are clustered within exon 9 and 20 (helical and kinase domains). Activating mutations in PIK3CA are found are found in a wide variety of human cancers including 27% urothelial bladder cancers, with a higher prevalence in low grade tumors. Up to 13.6% of renal pelvic urothelial carcinomas also harbor activating somatic mutations in PIK3CA gene. The role of PIK3CA mutations as prognosticators of outcome or predictors of therapeutic response awaits further evaluation.