NNMT and nonpapillary renal cell carcinoma: Nicotinamide N-methyltransferase (NNMT) has recently been shown to be an interesting candidate marker of aggressive ccRCC by two recent studies: Lebdai et al. demonstrated NNMT overexpression by western blotting in ccRCC tissues with high SSIGN scores [23], while Zaravinos et al. identified NNMT following a large meta-analysis of five published transcriptomic data sets and confirmed overexpression by IHC in ccRCC tissues [60].