The main predisposition of PMN formation in melanoma lies in the pulmonary recruitment of granulocytic myeloid-derived suppressor cells (G-MDSCs, CD11b<sup>+</sup>Ly6G<sup>+</sup> cells) induced by tumors, which increase vascular permeability by secreting matrix metalloproteinase-9 (MMP-9) and result in immunosuppression by secreting interleukin-10 (IL-10) in premetastatic lungs.