Consistent with these findings, the levels of macrophage colony-stimulating factor (M-CSF), an important cytokine that stimulates macrophage polarization into an M2-type macrophage, and its synergistic cytokine interleukin-34 (IL-34), are increased in fast-growing VS, suggesting their potential function as promoters of tumor progression (33). Here, IL34 is linked to neoplasm.