CSF1 and neoplasm: One of the most important mechanisms of tumor cell migration, induced by macrophages, has been elucidated in the past: it was shown that in in vivo experiments macrophages and tumor cells were both able to migrate to stimuli specific for only one of the cell types (i.e., colony-stimulating factor-1 (CSF-1) for macrophages and epidermal growth factor (EGF) for tumor cells), indicating the existence of a paracrine loop, leading to a synergistic relationship between migration of both macrophages and tumor cells [45].