CD8A and nasal cavity and paranasal sinus carcinoma: The aim of this study was to evaluate the presence of CD8+ TILs, PD-L1 expression and the expression of MLH1, MSH2, MSH6 and PMS2 as surrogate markers of MSI, in a series of poorly differentiated sinonasal carcinomas who had received conventional treatments, as possible indicators for treatment with immunotherapy.