Granulocyte colony-stimulating factor-producing ascending colon cancer as indicated by histopathological findings: report of a case.

Various types of granulocyte colony-stimulating factor (G-CSF)-producing malignant tumors have been reported. However, a G-CSF-producing colorectal cancer is rare. We present a case of G-CSF-producing ascending colon cancer. An 81-year-old man was referred to our hospital with right lower abdominal pain. A colon fiberscopy revealed an ascending colon tumor, and histological examination revealed tubular adenocarcinoma. He was admitted due to worsening abdominal pain. Although laboratory data showed an elevated white blood cell (WBC) count of 17000/mm3 with 77.8% neutrophils, elevated C-reaction protein (CRP) was insignificant (1.06 mg/dL), and he was afebrile. Because computed tomography indicated that the tumor penetrated into surrounding tissue, a semi-urgent ileocecal resection was performed. An abscess was not located. The tumor was staged as T3N2aM0 and as stage IIB according to the TNM classification. Microscopically, significant neutrophil infiltration between cancer cells was observed, suggesting the presence of a G-CSF-producing tumor. Immunohistochemical staining using a G-CSF antibody revealed cytoplasmic staining in cancer cells. The serum concentration of G-CSF upon admission was 334 pg/mL. After surgical resection, the WBC count decreased to within a normal range. These findings confirmed the diagnosis of G-CSF-producing ascending colon cancer. The prognosis of G-CSF-producing tumors is considered to be poor. Early diagnosis and surgical treatment are needed for patients with G-CSF-producing tumors, and continuous careful follow-up is required.