Imaging features of solid-cystic pancreatic neuroendocrine tumors

Abstract

Objective To discuss the imaging features of solid-cystic pancreatic neuroendocrine tumors (PNEN). Methods CT and MRI data of 38 pathologically diagnosed solid-cystic PNEN admitted in Changhai Hospital affiliated with Navy Medical University were retrospectively analyzed. The tumor location, major axis, shape, boundary, solid and cystic proportion, enhancement pattern, condition of cholangiopancreatic duct, vascular invasion, lymph nodes and organs metastasis were recorded, and the imaging features of PNEN were analyzed and summarized. Results Of 38 PNEN patients, only one case had two lesions including one solid lesion and one solid-cystic lesion, and 37 cases had only one solid cystic lesion including 6 with mainly cystic component and 31 with solid-cystic mixture. 22 of 38 lesions were located in head or neck of pancreas, and 16 were in body or tail of pancreas. The minimum of major axis was 1.1 cm, and the maximum was 13.3 cm, and the average was 5.5 cm. There were 23 round-like tumors, 2 oval tumors, and 13 irregular lesions; 25 lesions with clear margin, 13 with unclear margin. CT scan detected iso- to hypodense lesions, and speckled, nodular, cambered or eggshell calcification in 10 cases. The lesions were mainly manifested as low signal in T1WI, which were as inhomogeneous high signal and fluid high signal in T2WI. The solid component of all the lesions was strengthened at different degree after enhancement. 25 lesions showed obvious enhancement that was higher than that of normal pancreatic parenchyma. 13 lesions had no significant contrast enhancement that was similar to or lower than pancreatic parenchyma. 8 patients had mild dilations of main pancreatic duct and 1 case had mild dilation of common bile duct and intrahepatic bile duct. 5 cases were associated with the atrophy of pancreatic parenchyma with different degrees. 5 cases had adjacent organ infiltration, 3 cases had liver metastases and 3 cases had lymph node metastasis, 1 case had celiac axis, splenic artery and superior mesenteric vein invasion. 6 cases were associated with pancreatogenous portal hypertension. Conclusions Solid-cystic pancreatic neuroendocrine tumors can be easily misdiagnosed as other tumors of pancreas. Analyzing imaging characteristics and clinical data can be expected to improve diagnostic accuracy. Key words: Pancreas; Neuroendocrine tumors; Solid-cystic; Tomography, X-ray computed; Magnetic resonance imaging; Retrospective studies