VTCN1 and head and neck squamous cell carcinoma: TC results identified B7-H4+ and PD-L1+ most frequently in HNSCC and almost no NOM or SIN (B7-H4: NOM: 0%, SIN: 1%, and HNSCC: 55% and PD-L1: NOM: 2%, SIN: 10%, and HNSCC: 79%; Fig. 1b) with a significant mutually exclusive expression pattern between B7-H4 and PD-L1 in patients with HNSCC (55%, 52/94, p = 0.04: Fig. 1a-c; Table 1).