Two of the five T-cell infiltrated CAIX+ ccRCC tumors showed significant heterogeneity of intra-tumoral T-cell infiltration, with frequent CD8+ and CD4+ cells observed in some tumor regions with discrete CAIX expression but far fewer such cells in other contiguous CAIX-expressing areas (Figures 1F–I). This evidence concerns the gene CA9 and nonpapillary renal cell carcinoma.