Imaging presentation of pancreatic neuroendocrine neoplasms

Abstract

Pancreatic neuroendocrine neoplasms (P-NENs) are the second most common solid pancreatic neoplasms. P-NENs have a wide range of imaging features presentations and they can be detected with typical and atypical imaging presentations. Typical and atypical appearances can be explained by pathologic correlations. P-NENs are generally hypervascular lesions, showing a typical enhancement behavior after contrast media injection during imaging methods, but they could also have different imaging features, creating some difficulty in differential diagnosis. For this reason, radiologists should be aware of different imaging presentations of these neoplasms. Radiological evaluation has a critical role in P-NENs identification, characterization, and staging of these neoplasms, especially in those cases in which surgery is the treatment of choice. The present paper shows, indicating the underlying pathologic correlations, typical and atypical presentations of NENs. KEY POINTS: • P-NENs have a wide range of imaging features presentations, typical and atypical. • Pathology could help in better understanding the typical P-NENs appearance at imaging. • P-NENs are generally hypervascular lesions. • Radiological evaluation has a critical role in P-NENs identification and management. • Radiologists should know every type of different imaging presentation of P-NENs to better diagnose these kinds of lesions.

Keywords: P-NEN; Pancreatic neuroendocrine neoplasms; Pancreatic neuroendocrine tumors.

Fig. 1

Pancreatic neuroendocrine neoplasm (P-NEN). Histological analysis: neuroendocrine neoplasm (NEN) showing high cellularity during hematoxylin and eosin staining and high intralesional vascular network demonstrated by CD34 immunohistochemical staining

Fig. 2

Capsulated NEN. MRI study: the pancreatic head lesion is slightly hypointense on T1-weighted fat-saturated axial images (a) and presents diffusion restriction (b) on DWI (b = 800). In the late hepatospecific phase (c) with contrast medium (Gd-BOPTA), the common bile duct (C) is clearly visible and not dilated, since it is displaced but not compressed by the pancreatic head mass

Fig. 3

Non-functioning NEN. US and CEUS examinations: large hypoechoic mass (a) with small calcifications in the pancreatic head, causing upstream dilation of the Wirsung duct. This lesion is inhomogeneously hypervascularized at CEUS (b). CT examination: the pancreatic mass appears inhomogeneously hyperenhancing (c) in respect to the surrounding pancreatic parenchyma on dynamic phases. Dynamic MRI: inhomogeneous hypervascularity (d) of the pancreatic head mass

Fig. 4

Insulinoma. CT: a small insulinoma appearing as a hypervascular hyperdense nodule (a) in the pancreatic head. MRI: the small insulinoma is well detectable as a hyperintense nodule (b) on T2-weighted coronal images and hypervascular (c) in the dynamic phase

Fig. 5

Non-functioning NEN. CT examination: huge inhomogeneously hypervascular pancreatic body-tail mass with necrotic areas and intralesional calcifications. Liver metastatic involvement is present

Fig. 6

Non-functioning NEN. CT examination: huge inhomogeneously hypovascular pancreatic body-tail mass with necrotic areas and intralesional calcifications studied in the pancreatic (a) and venous (b) phases

Fig. 7

Non-functioning NEN. CT examination: small hypervascular pancreatic head mass irregular in shape invading the superior mesenteric vein with a small neoplastic thrombus studied in the pancreatic (a) and venous (b) phases

Fig. 8

Cystic NEN. CT examination: small cystic exophytic pancreatic tail mass with hypodense central area surrounded by thick hypervascular rim

Fig. 9

Thermolesion post-radiofrequency ablation (RFA). CT examination: hypodense avascular area in the right liver lobe (segment VI) related to coagulative necrosis post-RFA of small neuroendocrine metastasis