IL34 and neoplasm: Whatever the sources of macrophages, the tumor‐promoting influence of TAMs is strongly depended on the concentrations and roles of monocyte attractants and cytokines, which facilitate macrophages polarizing into tumor‐supportive TAMs in the TME.[35, 43] The colony‐stimulating factor 1 receptor (CSF‐1R, a transmembrane tyrosine kinase class III receptor) is a key regulator for controlling differentiation, proliferation and survival of macrophages.[12, 34] It has two ligands CSF‐1 and interleukin‐34 (IL‐34) to exert different functions, depending on the macrophage origin.