ARG1 and neoplasm: More recently, another attempt to distinguish between pro- and anti-tumour macrophages has been based on surface markers, where M1-like macrophages have been associated with the expression of CD40, CD74, MHC-II and phosphorylated STAT1, whereas M2-like cells express CD163, CD204, arginase-1 (ARG1) and phosphorylated STAT3 [14].