Granulocyte colony-stimulating factor (G-CSF) and granulocyte macrophage colony-stimulating factor (GM-CSF) are cytokines of particular interest in oncology from the perspective of neutropenia management (Mehta et al., 2015 [1]) and also as indirect activators of tumor-associated macrophages and modifiers of tumor microenvironment. The gene discussed is CSF2; the disease is neutropenia.