Multimodality Imaging of the Pancreatic Neuroendocrine Tumors.

Pancreatic neuroendocrine tumors (PNETs) are uncommon pancreatic masses which arise from amine precursor and uptake decarboxylation cells. They are classified as functional or nonfunctional based on the associated clinical symptoms. Insulinomas and gastrinomas are the most common functional tumors. PNETs are also classified based on their biologic behavior as benign or malignant. While most PNETs are sporadic, a small percentage are associated with syndromes such as multiple endocrine neoplasia type 1, von Hippel-Lindau syndrome, and are usually multiple in those cases. On imaging, most PNETs are circumscribed and hypervascular masses; however, larger tumors are often heterogeneous. The presence of calcification, cystic degeneration, and necrosis increases the likelihood of malignancy and carries a poor prognosis. Metastases have similar imaging appearance to the primary lesion and are most commonly seen in the liver, locoregional lymph nodes, and bone. This article reviews the pathologic and radiologic features of pancreatic neuroendocrine tumors as well as imaging mimics and their distinguishing features.