B-mode and contrast-enhancement characteristics of small nonincidental neuroendocrine pancreatic tumors

Abstract

Background and Objectives:Imaging of the pancreas for detection of neuroendocrine tumors is indicated as surveillance in multiple endocrine neoplasia type 1 (MEN1) or if typical clinical symptoms combined with hormone production raise the suspicion of a neuroendocrine tumor. Endoscopic ultrasound (EUS) is considered the best imaging modality to detect small pancreatic tumors. However, little is known about how small pancreatic neuroendocrine tumors (pNETs) present on EUS.Patients and Methods:In this multicenter study, we retrospectively analyzed the endosonographic characteristics of small pNETs which had been detected due to typical biochemistry and clinical symptoms or during surveillance of MEN 1. Only small pancreatic tumors ≤15 mm with histological confirmation as pNET were included. B-mode and contrast-enhanced ultrasound- and EUS patterns were analyzed.Results:Among 32 patients with histologically proven small pNETs, 7 patients had known MEN1. Among the pNETs, 20 were insulinoma, 2 gastrinoma, 3 glucagonoma, 6 nonfunctional in MEN1, and one PPoma. 94% of the pNET appeared hypoechogenic, only 1 isoechogenic and 1 hyperechogenic. After contrast injection, 90% of the pNETS showed hyperenhancement compared to the surrounding pancreatic parenchyma.Conclusion:The high spatial resolution of EUS allows detection and even cytological confirmation of pNET <7 mm diameter. Hypoechogenicity in B-mode and hyperenhancement after injection of contrast agents are endosonographic characteristics of small pNET and present in >90% of pNETs.

Serous pancreatic neoplasia, data and review

“…Specifically, extremely microcystic SPNs are considered rare, resembling a solid lesion in conventional US, but in fact a solid component was seen in the 55.7% of cases in our multicentre study. After contrast administration, these solid SPNs may resemble hypervascular solid lesions with homogeneous hyperenhancement, making differentiation from neuroendocrine neoplasms as difficult as it is crucial[ 35 , 36 ]. MRI may reveal a lesion’s true cystic nature[ 37 ].…”

“…Solid SPNs may mimic neuroendocrine tumours, renal metastases, intrapancreatic accessory spleens and other hypervascular pancreatic tumours[ 35 , 36 , 45 , 48 ]. Solid and pseudosolid SPNs are typically hypervascular and, therefore, hyperenhancing using CEUS[ 45 , 48 , 49 , 50 ].…”

Present status and perspectives of endosonography 2017 in gastroenterology

“…Sometimes, they may contain cystic components. Most of the tumors are well circumscribed and iso- or hypervascularized [ 90 ]. This can usually already be seen in an unenhanced Doppler EUS [ 91 ].…”

“…This can usually already be seen in an unenhanced Doppler EUS [ 91 ]. To date, CHI mode can improve the display of the hypervascularization of the tumor but this is not absolutely necessary [ 66 , 90 , 92 ]. In cases of hormone-active tumors, the clinical picture leads the way to the differential diagnosis of an unclear pancreatic lesion.…”

Diagnosis of Pancreatic Neuroendocrine Tumors

“…Contrast-enhanced EUS is helpful in characterizing small PNETs, which are incidentally found on other imaging modalities [ 46 ]. Over 90% of PNETs showed hypoechogenicity in B-mode and hyperenhancement after the injection of contrast agent in contrast-enhanced EUS ( Fig.…”