PDCD1 and nasal cavity and paranasal sinus carcinoma: While the treatment of advanced head and neck squamous cell carcinoma (HNSCC) has developed from platinum-based chemotherapy to molecular targeted therapy with agents, such as cetuximab (anti-EGFR antibody) and PD-1/PD-L1 Immune Checkpoint Inhibitors (ICIs) [55,56,57], sinonasal carcinomas are missing in global clinical trials [55,56,57].