A Case of Granulocyte Colony-stimulating Factor-producing Adenosquamous Carcinoma of the Ascending Colon.

We herein report a rare case of granulocyte colony-stimulating factor (G-CSF)-producing adenosquamous carcinoma of the ascending colon. An 80-year-old man was admitted to our hospital complaining of constipation and hypophagia. His medical history over the past nine years included chronic obstructive pulmonary disease, arteriosclerosis obliterans, and acute limb ischemia. He had no history of inflammatory bowel disease or other gastrointestinal conditions. Colonoscopy and contrast-enhanced computed tomography revealed a tumor in the ascending colon. Biopsies were obtained from five different areas of the lesion, all of which showed histological features consistent with squamous cell carcinoma. Notably, despite the absence of clinical signs of infection, the white blood cell count (WBC) and C-reactive protein (CRP) levels were elevated. Given these findings, a G-CSF-producing tumor was suspected. Subsequent measurement of serum G-CSF levels confirmed this elevation. Based on these findings, we initially suspected G-CSF-producing squamous cell carcinoma of the ascending colon, and proceeded with radical surgical resection. However, the final pathological examination revealed that the tumor contained a minor adenocarcinomatous component (approximately 1%), leading to a definitive diagnosis of adenosquamous carcinoma. We herein review the relevant literature and describe the diagnostic considerations, surgical management, and postoperative course of this rare case.