PTPN11 and neoplasm: CD47 is a protein widely expressed on the surface of many tumor cells, and studies have shown that tumor cells overexpressing CD47 can interact with SIRPα on the surface of macrophages or dendritic cells, leading to activation of downstream SHP-1 and SHP-2 phosphatases, and inhibition of macrophage phagocytosis, thereby promoting immune escape (47).