MLH1 and renal pelvis/ureter urothelial carcinoma: We retrospectively collected the clinical data of 150 consecutive patients with UTUC who underwent surgical resection at our institution between February 2012 and December 2020, and immunohistochemistry (IHC) of four MMRPs (MLH1, MSH2, MSH6, and PMS2) on all UTUC specimens was performed.