Jun Ushio, Kensuke Yokoyama, Alan Kawarai Lefor, Kiichi Tamada
Pancreatic neuroendocrine tumors are rare. In patients with functional PNETs, the excess hormones produced lead to a variety of hormone-related symptoms. Non-functioning tumors do not produce symptom-inducing hormones. Therefore, they are often discovered at an advanced stage with large tumors and metastatic spread. PNETs have a variable appearance on computed tomography scans and magnetic resonance imaging. With most functioning PNETs, Dynamic computed tomography scans and magnetic resonance imaging show well defined hypervascular small tumors. Imaging of other types of PNET show purely cystic, complex cystic or solid tumors. Functional imaging is useful both to detect the primary lesion and stage the disease. It is also useful to select candidates for peptide receptor radiometabolic treatment. Somatostatin receptor scintigraphy is the most available functional imaging technique. The gallium 68-SST analogue positron emission tomography scan is more sensitive, and is expected to be the future of functional imaging for PNETs. 18FDG PET/CT scan is useful for poorly differentiated tumors. The sensitivity of Carbidopa-assisted 18F-FDOPA PET/CT is better than somatostatin receptor scintigraphy for detecting nonfunctional PNETs. Endoscopic ultrasonography is superior to dynamic computed tomography scan to identify PNETS. Endoscopic ultrasonography-fine needle aspiration offers a high accuracy for the diagnosis of PNETs. However, tumors located in the pancreatic head and tumors with rich stromal fibrosis are associated with reduced sampling adequacy of endoscopic ultrasonography-fine needle aspiration. Some patients with poorly-differentiated PNETs have invasion of the pancreatic duct. Endoscopic retrograde cholangiopancreatography is useful for evaluating these patients.
