Intraductal papillary mucinous tumor of the pancreas: a pictorial essay.

Intraductal papillary mucinous tumor (IPMT) of the pancreas was identified and classified only recently. IPMT has a primarily intraductal, papillomatous growth pattern, which is associated with excessive mucin secretion and results in progressive ductal dilatation or cyst formation. The tumor occurs in four forms: segmental or diffuse involvement of the main pancreatic duct and macrocystic or microcystic involvement of a branch duct. In the past, many IPMTs may have been misdiagnosed as chronic pancreatitis because of their generally benign behavior. The correct diagnosis, once achieved only with endoscopic retrograde cholangiopancreatography (ERCP), can now be made with noninvasive imaging modalities, particularly computed tomography (CT) and magnetic resonance (MR) imaging. ERCP remains the imaging modality of choice for diagnosis of IPMT. With ERCP, the communication between the cystically dilated ductal segment or branch duct and the main pancreatic duct is easily demonstrated. However, reflux of contrast material due to an excess of mucin or an enlarged papillary orifice hinders filling of the ductal tree. Filling defects due to mucin globs or mural nodules are also important clues to the diagnosis. Bulging of the papilla into the duodenal lumen is virtually pathognomonic of IPMT and is well demonstrated with CT or MR imaging.