[Intraductal papillary mucinous tumor: imaging diagnosis]

We describe the specific findings for the diagnosis of cystic pancreatic tumors, serous cystic tumor (SCT), mucinous cystic tumor (MCT), and intraductal papillary-mucinous tumor (IPMT). The typical SCT is easy to diagnose as it is ball shaped and a honeycomb composition is seen on enhanced computed tomography (CT). SCT with large cysts on the periphery, or large cysts which themselves are the major part of the lesion, which we have often seen recently, causes diagnostic problems. The points for diagnosing such a lesion as SCT are 1) ERP does not show communication with the pancreatic duct, and 2) endoscopic ultrasound(EUS) reveals creeping small cysts inside the lesion. While MCT is ball shaped, covered with a relatively thick capsule, and has cysts that are convex into the cavity, IPMT has protruding cavities although it is also ball shaped. Since IPMT basically arises in the large pancreatic ductal system, the diagnosis is easy with by ERP. However, the problem is that histologically IPMT contains invasive cancer and/or hyperplasia, in addition to adenoma and/or adenocarcinoma. For the qualitative diagnosis of IPMT, it is important to measure the height of the tumor protrusions, for which EUS is excellent. Nonetheless, discrimination between adenoma and adenocarcinoma is not easy. Presently, IPMT lesions are differentiated as "adenoma or adenocarcinoma" and "hyperplasia."; Surgery is suggested for the former, and follow-up observation is appropriate for the latter.