CXCR4 and nonpapillary renal cell carcinoma: In the case of RCC-PDC2, the original patient tumor contained a tissue portion of ccRCC cells with eosinophilic cytoplasm and high NRN1/CXCR4 IHC staining, which feature was recapitulated in the established PDC spheroid culture and its PDCX tumor (Figure 2).