PDCD1 and head and neck squamous cell carcinoma: Immunotherapies targeting the programmed cell death protein 1 (PD1) pathway are approved by the Food and Drug Administration for the treatment of several metastatic or unresectable cancers including head and neck squamous cell carcinoma (HNSCC), but only ~20% of patients achieve a clinical benefit, highlighting the need for new therapeutic targets1,2,3.