Abstract:An 81‐year‐old female was admitted to our hospital with right upper abdominal pain and an abdominal mass. She has suffered from diabetes mellitus for 10 years. She did not have other past history. In addition, her serum level of CA19–9 was remarkably high, 39,000U/ml. Investigations of ultrasonography, computed tomography and angiography were done. These radiological findings showed that a large cystic mass, including the pancreatic head and body, had hypervascularity. Endoscopic retrograde cholangiopancreatography (ERCP) suggested that this cystic mass originated from the main pancreatic duct and was malignant. These studies revealed that this tumor might its histological diagnosis of intraoperative biopsy revealed adenosquamous carcinoma. There have been no reports about adenosquamous cell carcinoma with a large