PDCD1 and head and neck squamous cell carcinoma: Based on reports of successfully targeting the PD-1/PD-L1 axis in head and neck squamous cell carcinoma, lung cancer, renal cancer and melanoma,19, 20, 21, 22, 23 we evaluated the relevance of targeting this pathway in cSCC by assessing PD-1, PD-L1, PD-L2 and CD8 expression in cSCC, as well as determining the co-localization of CD8+ PD-1 T-cells with ligands PD-L1 and PD-L2.