PDCD1LG2 and head and neck squamous cell carcinoma: We here present an extensive analysis of PD-L1 and PD-L2 expression in two well defined independent cohorts (training set and testing set) of primary HNSCC tumor samples that included tumors derived from localized or locally advanced HNSCC located in the oral cavity, oropharynx, hypopharynx and larynx.