Schallenberg et al. sought to characterize the heterogeneity of molecular subtypes within MIBC bladder tumors by examining the tumor center and invasive front with IHC markers of molecular subtypes including FGFR3, CCND1, RB1, CDKN2A, KRT5, KRT14, FOXA1, GATA3, TUBB2B, EPCAM, CDH1, and vimentin [38]. The gene discussed is RB1; the disease is urinary bladder neoplasm.