CSF2 and neoplasm: The complex myelomonocytic checkpoints governing the differentiation of TAMs from myelomonocytic progenitors can broadly be considered as 3 steps: 1) IMC expansion and differentiation into MDSCs, 2) MDSC migration and differentiation into TAMs, and 3) TAM polarization, with each step being mediated by growth factors (GM-CSF (granulocyte macrophage colony stimulating factor); G-CSF), cytokines (IL-10, IL-6) and chemokines (CCL2, CCR5) released either by the tumor cells or the surrounding stroma (137).