Pancreatic neuroendocrine neoplasms: Magnetic resonance imaging features according to grade and stage

AIM To describe magnetic resonance(MR) imaging features of pancreatic neuroendocrine neoplasms(Pan NENs) according to their grade and tumor-nodes-metastases stage by comparing them to histopathology and todetermine the accuracy of MR imaging features in predicting their biological behavior.METHODS This study was approved by our institutional review board; requirement for informed patient consent was waived due to the retrospective nature of the study. Preoperative MR examinations of 55 Pan NEN patients(29 men, 26 women; mean age of 57.6 years, range 21-83 years) performed between June 2013 and December 2015 were reviewed. Qualitative and quantitative features were compared between tumor grades and stages determined by histopathological analysis.RESULTS Ill defined margins were more common in G2-3 and stage Ⅲ-Ⅳ PanN ENs than in G1 and low-stage tumors(P < 0.001); this feature had high specificity in the identification of G2-3 and stage Ⅲ-Ⅳ tumors(90.3% and 96%, 95%CI: 73.1-97.5 and 77.7-99.8). The mean apparent diffusion coefficient value was significantly lower in G2-3 and stage Ⅲ-Ⅳ lesions compared to well differentiated and low-stage tumors(1.09 × 10-3 mm2/s vs 1.45 × 10-3 mm2/s and 1.10 × 10-3 mm2/s vs 1.53 × 10-3 mm2/s, P = 0.003 and 0.001). Receiving operator characteristic analysis determined optimal cutoffs of 1.21 and 1.28 × 10-3 mm2/s for the identification of G2-3 and stage Ⅲ-Ⅳ tumors, with sensitivity and specificity values of 70.8/80.7% and 64.5/64%(95%CI: 48.7-86.6/60-92.7 and 45.4-80.2/42.6-81.3).CONCLUSION MR features of PanN ENs vary according to their grade of differentiation and their stage at diagnosis and could predict the biological behavior of these tumors.

Comparison of imaging-based and pathological dimensions in pancreatic neuroendocrine tumors

AIM To establish the ability of magnetic resonance(MR) and computer tomography(CT) to predict pathologic dimensions of pancreatic neuroendocrine tumors(Pan NET) in a caseload of a tertiary referral center.METHODS Patients submitted to surgery for Pan NET at the Surgical Unit of the Pancreas Institute with at least 1 preoperative imaging examination(MR or CT scan) from January 2005 to December 2015 were included and data retrospectively collected. Exclusion criteria were: multifocal lesions, genetic syndromes, microadenomas or mixed tumors, metastatic disease and neoadjuvant therapy. Bland-Altman(BA) and Mountain-Plot(MP) statistics were used to compare size measured by each modality with the pathology size. Passing-Bablok(PB) regression analysis was used to check the agreement between MR and CT.RESULTS Our study population consisted of 292 patients. Seventy-nine(27.1%) were functioning Pan NET. The mean biases were 0.17 ± 7.99 mm, 1 ± 8.51 mm and 0.23 ± 9 mm, 1.2 ± 9.8 mm for MR and CT, considering the overall population and the subgroup of non-functioning-Pan NET, respectively. Limits of agreement(LOA) included the vast majority of observations, indicating a good agreement between imaging and pathology. The MP further confirmed this finding and showed that the two methods are unbiased with respect to each other. Considering ≤ 2 cm non-functioning-Pan NET, no statistical significance was found in the size estimation rate of MR and CT(P = 0.433). PBR analysis did not reveal significant differences between MR, CT and pathology.CONCLUSION MR and CT scan are accurate and interchangeable imaging techniques in predicting pathologic dimensions of Pan NET.