FGFR3 and urothelial carcinoma: Key differences in the genetic features have been observed between these three classes; class 1 and 3 showed mutations in FGFR3, characteristic of well-differentiated, low-grade urothelial carcinoma cells [23,24], whereas class 2 harbored mutations in TP53, characteristic of advanced, high-grade urothelial carcinoma cells [24,25].