CTLA4 and nonpapillary renal cell carcinoma: In our effort to characterize the microenvironment of ccRCC tumors, we expanded our repertoire of 24 immune cell types to also include an angiogenesis signature [41] (Additional file 2: Table S1) and immunotherapeutic targets PD-1 (PDCD1), PD-L1 (CD274), and CTLA-4 (CTLA4).