CD274 and neoplasm: Previous studies have demonstrated high levels of PD-L1 expression both in ITAC (26%) and sinonasal SCC (30–46%) [76,77,78] and the presence of CD8+ tumor infiltrating lymphocytes (TILs), predominantly in the squamous type (up to 57%); even microsatellite instability (MSI) is reported in 21% of sinonasal SCC [79].