APOH and nonpapillary renal cell carcinoma: While the authors identified proteins that differentiated sporadic ccRCC and VHLD patients from healthy controls, as well as sporadic ccRCC patients from VHLD patients with distinct ccRCC diagnoses backgrounds, the authors chose to validate two proteins—A1AT and APOH—which were found to be elevated in the urine of VHLD-ccRCC-positive patients relative to the other three groups.