HIF1A and nonpapillary renal cell carcinoma: Molecular studies have identified several genes that are causally implicated in the carcinogenesis of ccRCC, including von Hippel-Lindau (VHL) [7], hypoxia-inducible factor-1a (HIF1a) [8], vascular endothelial growth factor (VEGF), and epidermal growth factor receptor (EGFR) [9].