PDCD1 and neoplasm: Immunotherapy using immune checkpoint blockade such as that of PD-1, PD-L1, and CTLA-4 inhibitors have demonstrated durable anti-tumour response in several cancer types including melanoma [1, 2], non-small cell lung carcinoma [3–5], head and neck squamous cell carcinoma [6], urothelial carcinoma [7], renal-cell carcinoma [8], and Hodgkin lymphoma [9].