Granulocyte-colony-stimulating factor-producing gastric metastasis from large cell type lung cancer

We report a case of granulocyte-colony-stimulating factor (G-CSF)-producing gastric metastasis from large cell type lung cancer. A 73-year-old man presented with severe anemia and leukocytosis that appeared 8 months after surgery for early lung cancer. Gastroendoscopy demonstrated a protruding circumscribed tumor with blood clot in the middle part of the stomach. The pathological finding from biopsy specimens revealed gastric metastasis of large cell carcinoma of the lung. Positron emission tomography/computed tomography demonstrated uptake in the bone; however, myeloid metastasis was negative with bone marrow biopsy. Serum level of G-CSF was elevated. We performed partial gastrectomy for hemostasis. After surgery, the hemoglobin, leukocyte count and serum level of G-CSF were within the expected normal limit. Immunohistological examination of G-CSF was positive in the resected specimen. The patient was discharged 22 days after the operation and has been followed up from 3 months after surgery to the present time. G-CSF-producing tumors have been reported to cause remarkable peripheral leukocytosis and neutrophil production in bone marrow. They have been reported in various types of malignancies and are usually associated with a poor prognosis.