The recent classification of UTUC into five mutational subtypes—the hypermutated, the TP53/MDM2-mutated, the RAS-mutated, the FGFR3-mutated, and the triple-negative—could serve as an additional tool for the better diagnosis and management of UTUC [53]. This evidence concerns the gene MDM2 and renal pelvis/ureter urothelial carcinoma.