In the paracrine pathway, IL-34 produced by tumor cells and/or immune cells triggers M-CSF1-R signaling in tumor-associated macrophages (TAMs), thereby promoting recruitment of TAM to the tumor area, facilitating the formation of new blood vessels and the exosmosis of immunosuppressive cells (Figure 5) (Mantovani et al., 2017). This evidence concerns the gene IL34 and neoplasm.