As patients with previous history of pancreatitis were excluded from the study, CT findings allowed correct characterization of only 60% of cystic pancreatic masses. Among the remaining 40%, 15-20% of the wrong diagnoses could not be corrected by means of CT, given the patterns shown by the tumors. In 20-25% of the cases, a nonspecific diagnosis of cystic mass was made.

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.

The aim of this study was to assess the ability of spiral CT to adequately characterize the nonfunctioning endocrine tumors (NFETs) of the pancreas, distinguishing this lesion from the other pancreatic tumors. The spiral CT examinations of 21 cases of histologically proven NFETs, along with those of 29 cases of other pancreatic tumors and tumor-like lesions, were retrospectively reviewed in a blinded fashion by two radiologists, in order to correctly classify the lesions, highlighting the typical signs reported in the literature. Discordant cases were further analyzed in the presence of a third radiologist. The final diagnosis was acquired by means of a majority or overall consensus. The histopathologic examination was considered the gold standard. The sensitivity, specificity, and positive and negative predictive values of CT were calculated. After the consensus evaluation, the correct diagnosis was reached in 72% of cases, with 10% of nonspecific diagnoses of solid pancreatic tumor and 18% of wrong diagnoses. The sensitivity and specificity of spiral CT in identifying NFETs were 66.6 and 82.7%, respectively. The positive and negative predictive values were 73.7 and 77.4%, respectively. In up to 70% of cases the NFET demonstrates a typical aspect of a mass hyperdense in the arterial contrastographic phase eventually associated with hyperdense hepatic metastases in more than half of the patients. This finding does allow the diagnosis of NFET but without certainty indeed, since other tumors can show a similar densitometric behavior and among them particularly the ductal adenocarcinoma. On the other hand, both the solid, hypovascularized NFETs, and the cystic form, cannot be differentiated from the other solid and cystic tumors of the pancreas.