KRT14 and renal pelvis/ureter urothelial carcinoma: To characterize protein‐based UTUC subtypes, the expression of three basal (CK5, CK14, and CD44) and three luminal (CK20, FOXA1, and GATA3) differentiation markers of the urothelium was assessed in a cohort of 163 invasive samples, referred to as the ‘German cohort’.