Tumor-derived signals, such as Macrophage-Colony Stimulating Factor (M-CSF/CSF-1), Monocyte Chemoattractant Protein-1 (MCP-1), or Chemokine (C-C motif) Ligand-2 (CCL2) entails the accumulation of M2 at the tumor site. The gene discussed is CSF1; the disease is neoplasm.