PDCD1 and head and neck squamous cell carcinoma: As shown in Figure 6E, we divided the HNSCC patients into four groups, and HNSCC patients in the low risk group based on PHILTlncRNAs and PD-1 low expression had the best prognosis compared with the other three groups, while the HNSCC patients in high risk group and PD-1 low expression had the worst prognosis compared with the other three groups.