PDCD1 and neoplasm: Based on the concept that higher mutation loads could yield to improved T-cell recognition of tumors via increased neoantigen production, tumor mutational burden (TMB), defined as the number of somatic mutations per megabase (mut/Mb) [153], was investigated as a predictive biomarker of response to PD-1/PD-L1 ICB in several solid malignancies [154,155,156].