Of them, 23 patients had already underwent measurement of serum G-CSF expression, as they were suspected of having G-CSF-producing lung cancer due to the presence of fever, increased WBC count, high inflammatory response, and diffuse accumulation of 18F-fluorodeoxyglucose (FDG) in the bone marrow as shown on positron emission tomography/computed tomography (PET/CT) scan. Here, CSF3 is linked to lung cancer.