Is the combination of MR and CT findings useful in determining the tumor grade of pancreatic neuroendocrine tumors?
PURPOSE
To retrospectively elucidate the findings useful in determining the tumor grade of pancreatic neuroendocrine tumors (PNETs) by combined assessment of magnetic resonance (MR) and dynamic computed tomography (CT) images.


MATERIALS AND METHODS
Eighty-nine patients with PNETs (96 lesions) were included, and classified as G1, 59; G2, 29; and G3, 8 lesions. Image analysis included lesion diameter, shape, enhancement pattern on arterial phase (AP) and delayed phase CT images, calcification, cystic portion, main pancreatic duct dilatation, signal-intensity on T1-, T2-weighted MR images, and appearance of apparent diffusion coefficient (ADC).


RESULTS
Significant differences among G1, G2, and G3 groups were noted in tumor maximal diameter (p < 0.0001), shape (p < 0.0001), enhancement pattern on AP image (p < 0.0001), cystic portion (p = 0.012), and ADC finding. In multivariate analysis, ADC finding was the independent factor (p = 0.002). The combination findings of low ADC ratio (ADC value of the lesion/ADC value of the parenchyma <0.94), not homogeneous hyper-attenuation, lobulated shape, and hyper-intensity on T2-weighted image were suggestive of G2 or G3 with a probability of 100%. Conversely, all lesions with high ADC ratio and small size (≤25 mm) belonged to the G1 group.


CONCLUSION
Combined assessment of MR and CT findings could improve the prediction of tumor grading in PNETs.
['Toshima|Fumihito|F|', 'Inoue|Dai|D|', 'Komori|Takahiro|T|', 'Yoshida|Kotaro|K|', 'Yoneda|Norihide|N|', 'Minami|Tetsuya|T|', 'Matsui|Osamu|O|', 'Ikeda|Hiroko|H|', 'Gabata|Toshifumi|T|']
D000293:Adolescent D000328:Adult D000368:Aged D000369:Aged, 80 and over D002648:Child D005260:Female D006801:Humans D008279:Magnetic Resonance Imaging D008297:Male D008875:Middle Aged D064847:Multimodal Imaging D060787:Neoplasm Grading D018358:Neuroendocrine Tumors D010190:Pancreatic Neoplasms D012189:Retrospective Studies D014057:Tomography, X-Ray Computed D055815:Young Adult
Pancreatic neuroendocrine tumors Computed tomography (CT) Magnetic resonance imaging (MRI) Neuroendocrine carcinoma Neuroendocrine tumors G1 Neuroendocrine tumors G2