MKI67 and nonpapillary renal cell carcinoma: Ki-67 is a nuclear antigen that is present in all cycling human cells and is a marker of cell proliferation.[15] Increased expression of Ki-67 has been associated with higher nuclear grade and worse prognosis in ccRCC.[16] Several recent studies suggest that Ki-67 expression could serve as an independent predictor of DFS in localized ccRCC on multivariate analysis[17, 18] and that it may represent the true “molecular grade” of ccRCC.[18]