Programmed Death Ligand 1 in Non-Clear Cell Renal Cell Carcinoma and Correlation with Tumor Microenvironment and Prognostic Factors

Non-clear cell renal cell carcinomas (non-ccRCC) are relatively uncommon tumors compared with clear cell RCC. Targeting immune checkpoints such as Programmed Death / Programmed Death Ligand 1 (PD1/PD-L1) axis has been promising. In addition intratumoral PD-L1 expression is a predictor of poor prognosis in some cancers. In this study we aimed to characterize the association between PD-L1 expression and clinico-pathological prognostic factors and to evaluate lymphocyte density displaying the PD-1, CD4, and CD8 expression in the tumor microenvironment in non-ccRCC. Immunohistochemical analysis was performed for the expression of PD-L1, PD-1, CD4 and CD8 on tissue microarray sections. PD-L1 positivity rate was found to be %24. Dense lymphocytic infiltration staining with PD-1, CD4, and CD8 was significantly high in PD-L1 positive tumors. There was no correlation between PD-L1 expression and any of the tested negative prognostic factors. Only the rate of WHO ISUP grade 3–4 tumors was considerably higher in PD-L1-positive cases than that in negative ones. Further evaluation of PD-L1 as a potential predictive biomarker in larger series and standardization of staining procedures and scoring methods are warranted. At the mean time pathologists should be aware of the importance of lymphocytic infiltration in the tumor microenvironment, which potentially may be a predictive marker for targeted therapy.