CD274 and nasal cavity and paranasal sinus carcinoma: <h4>Aim</h4>To characterize the expression of CD8 + T cells, CD68 + macrophages, and PDL1 in HPV-related multiphenotypic sinonasal carcinoma (HMSC) and evaluate their correlations with clinical outcomes.<h4>Materials and methods</h4>This retrospective cross-sectional study analyzed 27 HMSC cases.