Purpose: To investigate staging accuracy of MR for pancreatic neuroendocrine neoplasms (PNETs) and imaging findings according to the tumor grade.
Materials and methods: Our study consisted of 39 patients with PNET G1 (n = 24), PNET G2 (n = 12), and pancreatic neuroendocrine carcinoma (PNEC) (n = 3). All underwent preoperative MRI. Two radiologists retrospectively reviewed MR findings including tumor margin, SI on T2WI, enhancement patterns, degenerative change, duct dilation, and ADC value. They also assessed T-stage, N-stage, and tumor size. Statistical analyses were performed using Chi square tests, ROC analysis, and Fisher's exact test.
Results: Specific findings for PNEC or PNET G2 were ill-defined borders (P = 0.001) and hypo-SI on venous- and delayed-phase (P = 0.016). ADC value showed significant difference between PNET G1 and G2 (P = 0.007). The Az of ADC value for differentiating PNET G1 from G2 was 0.743. Sensitivity and specificity were 70% and 86%. Accuracy for T-staging was 77% (n = 30) and 85% (n = 33), and for N-staging was 92% (n = 36) and 87% (n = 34) with moderate agreement. T-stage showed significant difference according to tumor grade (P < 0.001), although there was no significant difference in tumor size or N-stage.
Conclusion: Ill-defined borders and hypo-SI on venous- and delayed-phase imaging are common findings of higher grade PNET, and ADC value is helpful for differentiating PNET G1 from G2. MR is useful for preoperative evaluation of T-, N-stage. Tumor size of PNET and T-stage showed significant difference according to tumor grade.