Nonhypervascular Pancreatic Neuroendocrine Tumors: Differential Diagnosis from Pancreatic Ductal Adenocarcinomas at MR Imaging—Retrospective Cross-sectional Study

Abstract

Purpose To determine useful magnetic resonance (MR) imaging features to differentiate nonhypervascular pancreatic neuroendocrine tumors (PNETs) from pancreatic ductal adenocarcinomas (PDACs). Materials and Methods The institutional review board approved this retrospective study and waived the informed consent requirement. Seventy-four patients with surgically confirmed PNETs and 82 patients with PDACs who underwent gadobutrol-enhanced MR imaging were included. Two radiologists independently evaluated the morphologic characteristics and temporal enhancement patterns of each tumor. Quantitative analysis, including measurement of tumor size, maximal upstream parenchymal thickness (MUPT), contrast-to-noise ratio, and apparent diffusion coefficient values, was performed. Uni- and multivariate logistic regression analyses were performed to identify relevant features to differentiate between PNETs and PDACs. Results On the basis of arterial enhancement, 38 PNETs (51%, 38 of 74) were hypervascular and 36 PNETs (49%, 36 of 74) were nonhypervascular. At MR imaging, nonhypervascular PNETs showed significantly higher frequencies of a well-defined margin, portal hyper- or isoenhancement, and MUPT of 10 mm or greater but lower frequencies of ductal dilatation, vascular invasion, and peripancreatic infiltration when compared with PDACs (P < .05 for all). At multivariate analysis, a well-defined margin and portal hyper- or isoenhancement were independent significant differentiators of PNETs from PDACs (odds ratio, 20.3 and 16.1, respectively). When applying the criteria of a well-defined margin and portal hyper- or isoenhancement, 64% of sensitivity and 99% of specificity were observed for the differential diagnosis of PNETs from PDACs. Conclusion A well-defined margin and hyper- or isoenhancement in the portal venous phase are useful MR imaging features that are more common in nonhypervascular PNETs and may help discriminate nonhypervascular PNETs from PDACs. RSNA, 2017 Online supplemental material is available for this article.

Imaging diagnosis and staging of pancreatic ductal adenocarcinoma: a comprehensive review

“…Pancreatic neurendocrine tumors (PNETs) account for 1-3% of all pancreatic neoplasms, most commonly in the fourth-sixth decades of life [94,95]. In contrast to PDAC, PNETs tend to show a well-circumscribed mass, iso-to hyperenhancing relative to the normal pancreas and less frequently associated with upstream MPD dilatation and distal pancreatic atrophy [94,96,97] (Fig. 13).…”

Differentiation of atypical pancreatic neuroendocrine tumors from pancreatic ductal adenocarcinomas: Using whole‐tumor CT texture analysis as quantitative biomarkers

“…Contrast‐enhanced CT is currently widely used for evaluating abdominal lesions because of its broad availability and convenience . Jung Hoon and Sun Kyung et al have evaluated the imaging characteristics of atypical hypovascular PNET and PDAC, respectively. They found duct dilatation in CT may be a helpful predictor for PDAC .…”

“…11 A well-defined margin and hyperor iso-enhancement on portal phase may be useful MR imaging features for atypical hypovascular pNETs. 12 However, the current identification of pancreatic tumors is mostly based on anatomical imaging characteristics, which is still insufficiently specific due to overlapping imaging features and easily affected by subjective of radiologists. Therefore, a method to quantitatively assess differences between tumors is urgently needed.…”

Abdominal Manifestations of Neuroendocrine Tumors

“…They may also be infiltrative and heterogeneous. [38][39][40][41]46 The most common diagnostic dilemma for nonhypervascular PNET is with pancreatic adenocarcinoma (PDAC) (►Figs. 5 and 6).…”