Tumour immune microenvironment in primary and metastatic papillary renal cell carcinoma.

We found PD-L1 expression in up to one-quarter of primary and metastatic papillary RCC. On univariate analysis, CD8/FoxP3 ratio >1 was associated with favourable outcome, whereas papillary RCCs with high numbers of dual CD8/Ki-67-positive lymphocytes showed an increased likelihood for tumour progression and overall and cancer-related mortality. The association of CD8/FoxP3 ratio >1 and high count of CD8/Ki-67 with outcome remained significant on multivariate analysis when adjusting for stage, grade and patient's age.