Computed tomography and magnetic resonance imaging features of pancreatic neuroendocrine tumors / 中华消化外科杂志

ABSTRACT

Objective To investigate the features of computed tomography (CT) and magnetic resonance imaging (MRI) on pancreatic neuroendocrine tumors (pNENs).Methods The retrospective and descriptive study was adopted.The clinicopathological data of 33 patients with pNENs who were admitted to the Tongji Hospital of Tongji Medical School of Huazhong University of Science and Technology between May 2012 and February 2016 were collected.All the patients underwent plain and enhanced scans of CT and MRI.Observation indicators(1) overall imaging findings and pathological results of pNENs,(2) imaging findings of functional pNENs,(3) imaging findings of non-functional pNENs.Main analysis indicators included tumor diameter,location,boundary,density,cystic degeneration,enhancement,signal,calcification,with or without pancreaticobiliary duct dilation,with or without surrounding tissues invasion,lymph node and distant organ metastases.Results (1) Overall imaging findings and pathological results of pNENsof 33 patinets with pNENs,24 underwent CT examination,3 underwent MRI examination and 6 underwent CT and MRI examinations.Tumors of 33 patients were solitary with a diameter of 0.6-16.0 cm.Ten,1,13 and 9 tumors were respectively located at the head of pancreas,uncinate process of pancreas,body of pancreas and tail of pancreas.Thirty-three patients were diagnosed as pNENs by pathological examination,including 20 with functional pNENs (insulinoma) and 13 with non-functional pNENs,and G1,G2 and G3 were respectively detected in 24,7 and 2 patients.The coincidence rate between preoperative CT or MRI examination and pathological examination was 90.9％ (30/33).One,1 and 1 patients were misdiagnosed as pancreatic cancer,enlargement of peripancreatic lymph nodes and duodenal gastrointestinal stromal tumor,respectively.(2) Imaging findings of functional pNENstumor diameter of 20 patients with functional pNENs was 0.6-3.0 cm with an average diameter of 1.5 cm.Fòur,10 and 6 tumors were respectively located at the head of pancreas,body of pancreas and tail of pancreas.Of 20 patients with functional pNENs,tumors of 19 patients showed clear boundary and 1 showed unclear boundary,and tumors of 18 patients had uniform density and 2 had uneven density with cystic degeneration,without the occurrence of calcification.Of 20 patients undergoing dynamic enhanced scans,tumors of 19 patients demonstrated obvious enhancement in arterial phase and slightly obvious enhancement or were equal to normal pancreatic tissues in portal vein phase and lag phase,and tumor of 1 patient demonstrated slight enhancement in arterial phase and was equal to or less than normal pancreatic tissues in portal vein phase and lag phase.Tumors in 3 patients undergoing MRI scans were manifested as hypointensity on T1-weighted imaging (T1WI),hyperintensity on T2WI and hyperintensity on DWI (b =1 000 s/m2),with clear imaging.Of 20 patients,1 was accompanied with atrophy of pancreatic tissues at distal tumor,pancreatic duct dilatation,multiple retention cyst and enlargement of lymph nodes around the hepatic artery.(3) Imaging findings of non-functional pNENstumor diameter of 13 patients with non-functional pNENs was 1.5-16.0 cm with an average diameter of 5.0 cm.Six,1,3 and 3 tumors were respectively located at the head of pancreas,uncinate process of pancreas,body of pancreas and tail of pancreas.Of 13 patients with non-functional pNENs,tumors of 11 patients showed clear boundary and 2 showed unclear boundary,tumors of 3 patients had uniform density and 10 had uneven density with cystic degeneration,and tumors of 2 patients had calcification.Of 13 patients undergoing dynamic enhanced scans,tumors of 12 patients demonstrated obvious enhancement in arterial phase,continuous enhancement in portal vein phase and lag phase and less obvious enhancement at cystic degeneration area,with marked enlargement of supplying arteries and draining veins in partial tumors.Tumor of 1 patient demonstrated slight enhancement,and its enhancement was slightly less than normal pancreatic tissues in arterial phase,portal vein phase and lag phase,with unclear boundary.Results of MRI scans in 6 patients showed that tumors of 4 patients were manifested as hypointensity on T1WI,slight hyperintensity or mixed signal on T2WI and hyperintensity on DWI (b =1 000 s/m2),and tumors of 2 patients were manifested as hypointensity on T1WI,hypointensity on T2WI and hyperintensity on DWI (b =800 s/m2).Of 13 patients with non-functional pNENs,4 had pancreaticobiliary duct dilation and 7 had local tissues invasion or distant organ metastasis (4 with liver metastasis,1 with peripanereatic lymph node metastasis,1 with liver and peripancreatic lymph node metastases and 1 with liver metastasis combined with splenic venous and arterial invasion),including 1 in G1,4 in G2 and 2 in G3.Of 5 patients with tumor diameter ＞ 5.0 cm,4 were complicated with liver or lymph node metastases.Conclusions CT and MRI features of pNENs have a certain characteristics.For functional pNENs,benign and solid tumor is common,with clear boundary and smaller diameter.For non-functional pNENs,tumor size is bigger and cystic necrosis occurs within the tumor,with various enhancements.