In the case of RCCs, standardization of protein expression quantification, not only for WT1, but other tumor-associated antigens (CTLA4, PD1/PDL1) as well, is mandatory for further progress and will require extensive characterization of staining patterns, with both specificity and sensitivity, for the plethora of commercially available IHC antibodies, on larger RCC populations and for individual RCC subtypes. Here, CTLA4 is linked to renal cell carcinoma.