PDCD1 and neoplasm: Importantly, HPV(+) tumors possess a unique tumor-immune landscape, including differing types, proportions, and functions of immune cells when compared with HPV(−) tumors and recent studies demonstrate these HPV(+) tumors harbor functional PD-1+TCF-1+CD45RO+ stem-like CD8 T cells suggesting that these patients with HNSC retain the ability to respond to PD-1 checkpoint blockade (64–68).