Recent studies have revealed the expression of CD244 on monocyte-lineage cells, suggesting a positive correlation between the expression level of CD244 on tumor-infiltrating monocytes and their immunosuppressive phenotype, such as the expression of arginase-1 (ARG-1), interleukin-10 (IL-10), and transforming growth factor-β (TGF-β) [21]. Here, ARG1 is linked to neoplasm.