PDCD1 and head and neck squamous cell carcinoma: Patients with recurrent or metastatic disease have a very poor prognosis and systemic treatment with the combination of cetuximab, platinum and fluorouracil is standard first line treatment.3 Recently, immune checkpoint inhibitors, i.e. antibodies targeting the programmed cell death protein-1 (PD-1)/programmed death ligand 1 (PD-L1) signalling pathway have been approved by the FDA for second-line treatment of HNSCC.4 Nivolumab, a PD-1 inhibitor, demonstrated improved response rate and overall survival compared to conventional chemotherapy5,6 in a randomised phase III trial.