SIRPA and neoplasm: CD47 was originally identified in 1987 on red blood cells (RBCs).21 Until 2000, CD47 was viewed as a “marker of self” on murine RBCs that binds to SIRPα on phagocytes.22,23 It was confirmed as a tumor phagocytosis checkpoint that delivers a “don’t eat me” signal during immune evasion in 2019, and CD47-targeting antibodies and inhibitors are currently in clinical trials.