MRI appearance of pancreatic neuroendocrine neoplasms correlation with pathological grade: comparative study

Abstract

Objective To analyze MR imaging appearance of pancreatic neuroendocrine neoplasms(pNEN) and to investigate the practical value of MR imaging appearance in predicting pathological grade of pNEN. Methods All data of 35 patients with pathologically proven pNEN were retrospectively reviewed. MR examinations of the abdomen were performed on all these patients before operation and the data of clinical, pathological and MR imaging were intact. Both plain scan and contrast-enhanced MR scan were performed on each patient. Histopathological grade of pNEN was defined as: G1, G2, and G3 according to World Health Organization classification of tumours of the digestive system guidelines (2010). Image analysis included tumor location, number, size, shape, lesion margins, signal intensity, enhancement pattern, main pancreatic duct dilatation, extrapancreatic spread, and metastases of lymph node and liver. The comparison of quantitative index between G1 and G2 group was performed with t test. Categorical variables were tested using Fisher exact test. Results Thirty five lesions were found in 35 patients, with 14 lesions in G1, 19 lesions in G2, and 2 lesions in G3.Thirty three lesions appeared as a solid mass, and 2 lesions appeared as a cystic lesion. Significant gender-based difference was found between G1 group and G2 group (P 0.05). Of the 35 lesions, 27 lesions were round in shape, while other 8 lesions were irregular. There were 18 lesions with clear margin, and the margins in other 17 lesions were blurred. Main pancreatic duct dilatation was found in 3 cases (1 in G2, 2 in G3). Significant differences in tumor diameter, shape, margin, signal intensity on precontrast images, extrapancreatic spread and metastases were found between G1 group and G2 group (P<0.05). No significant difference was found in main pancreatic duct dilatation or signal intensity on all enhancement phases between G1 group and G2 group. The 2 lesions in G3 group appeared mild contrast enhancement with degrees lower than the pancreas in all enhancement phases. Conclusion MR imaging features such as tumor diameter, shape, margin, signal intensity on precontrast images, extrapancreatic spread and metastases may preoperatively predict the pathological graden of pNEN. Key words: Pancreatic neoplasms; Neuroendocrine neoplasms; Magnetic resonance imaging