Objective:

To investigate the

computed tomography (CT) and magnetic resonance imaging (MRI) features of pancreatic neuroendocrine neoplasm (pNEN).

Methods:

CT and MRI data of 143 patients with pNEN confirmed by surgery and pathology from February 2009 to September 2020 were retrospectively analyzed. The lesions were divided into four groups including neuroendocrine tumor (NET) G1

NET G2

NET G3 and neuroendocrine carcinoma (NEC) G3. Image analysis included tumor location

size

shape

edge

density or signal intensity

enhancement characteristics

main pancreatic duct dilatation

peripheral invasion and metastasis.

Results:

A total of 149 lesions were detected in 143 patients. The number of NET G1

NET G2

NET G3 and NEC G3 lesions was 63

74

8 and 4

respectively. NEC G3 group had the largest lesion (average diameter was 5.75 cm)

and NET G1 group had the smallest lesion (average diameter was 2.24 cm). There were 127 (85.2%) round-like lesions and 22 (14.8%) irregular lesions. 130 (87.2%) lesions were iso-density on CT plain scan

and 19 (12.8%) lesions were slightly low density. 124 (83.2%) lesions appeared hyperintense or slightly high signal intensity on T2-weighted imaging (T2WI)

146 (98.0%) lesions appeared moderately or slightly hypointense on T1-weighted imaging (T1WI)

and all 130 lesions showed high signal intensity on diffusion-weighted imaging (DWI). Clear margin in 76 (51.0%) lesions

cysts in 57 (38.3%) lesions

calcification in 22 (14.8%) lesions

pancreatic duct dilatation in 14 (9.4%) lesions

distal pancreatic atrophy in 9 (6.0%) lesions

peripancreatic invasion in 30 (20.1%) lesions

lymph node metastasis in 14 (9.4%) lesions

and liver metastasis in 15 (10.1%) lesions were found. After contrast-enhancement

92 (61.8%) lesions showed continuous significant enhancement on CT images

and 115 (77.2%) lesions showed obvious enhancement on arterial phase images with its degrees higher than the pancreas and continuous contrast-enhancement. Four lesions of NEC G3 appeared slightly contrast enha

ncement with degrees lower than the pancreas all the time.

Conclusion:

The typical CT and MRI manifestations of pancreatic neuroendocrine neoplasms are round-like nodules or masses. The lesions are equal or slightly low density on CT plain scan and low or slightly low signal intensity on T1WI. After contrast enhancement

most of the low-grade tumors showed obvious continuous enhancement

while most of the high-grade neoplasms showed slightly contrast enhancement on all phase images with its degrees lower than the pancreas.