[Case of main duct-intraductal papillary mucinous carcinoma (pancreatobiliary type) causing 4-mm dilatation of the pancreatic duct].

A 77-year-old woman with mild dilatation (4mm) of the main pancreatic duct was referred to our hospital. Contrast-enhanced computed tomography revealed segmental dilatation of the main pancreatic duct in the pancreatic tail, but no mass was noted in the pancreas. Endoscopic ultrasonography showed low papillary lesions in the dilated pancreatic duct. Cytological analysis of the pancreatic juice revealed adenocarcinoma. Distal pancreatectomy was performed for a diagnosis of main duct-intraductal papillary mucinous cancer (MD-IPMC) of the pancreatic tail. Histological findings indicated pancreatobiliary (PB)-type non-invasive IPMC. Although the patient did not meet the diagnostic criteria for intraductal papillary mucinous neoplasms (IPMNs), her final diagnosis was PB-type non-invasive IPMC. Because PB-type IPMNs display poor mucin production, pancreatic duct dilatation is sometimes mild and requires careful assessment for accurate diagnosis.