PDCD1 and neoplasm: In CM, several studies have shown that certain immunoPET tracers such as 64Cu-DOTA-anti-PD-1-mAb or 64Cu-NOTA-PD-1-mAb may be successfully used for the non-invasive imaging of PD-1/PD-L1 expression and for examining the extent of tumor-infiltration of lymphocytes in tumor tissues [296,297].