Asano et al. proposed the following 4 criteria for diagnosing G-CSF-producing tumors: (1) marked granulocytosis, mainly consisting of mature neutrophils, (2) elevated serum and urine G-CSF levels, (3) normalization of granulocyte count and G-CSF level following tumor removal, and (4) demonstration of increased G-CSF in the tumor [4]. The gene discussed is CSF3; the disease is neoplasm.