Neuroendocrine Tumors: A Review of CT and MRI Findings

Neuroendocrine tumors, including pancreatic neuroendocrine tumors and carcinoid tumors, are rare neoplasms that arise from a common precursor, the APUD cell (amine precursor uptake and decarboxylation). All neuroendocrine tumors have the ability to produce and secrete peptides and hormones, although many do not. Functional tumors, those that secrete hormones, tend to present early with small tumors due to the resulting clinical syndrome related to the excess hormone secretion. Conversely, non-functioning tumors (those without hormone secretion) tend to present later and with larger tumor size. For this reason, functional tumors can be sometime be very difficult, if not impossible, to identify on imaging due to small size.