CD274 and head and neck squamous cell carcinoma: Our findings that tumor cells expressing Sema4D+ve/high correlated positively with a non-inflamed dense fibrotic stroma and inversely with Sema4D+ve/high TAIs, triggered the question; if HNSCC tumors expressing high Sema4D represent a distinct tumor phenotype other than the inflamed, PD-L1 positive tumors.