n euroendocrine t umors: Role of Imaging in Diagnosis and Management 1

Gastroenteropancreatic neuroendocrine tumors (GEP- NETs) are a heterogeneous group of neoplasms that arise from cells of the diffuse neuroendocrine system and are characterized by a wide spectrum of clinical manifesta- tions. All NETs are potentially malignant but differ in their biologic characteristics and the probability of metastatic disease. The pathologic classification of these tumors re - lies on their proliferation and differentiation. In the past decades, several nomenclatures have been proposed to stratify neuroendocrine tumors, but the World Health Or- ganization classification is the one that is most widely ac - cepted and used. The diagnosis of neuroendocrine tumor relies on clinical manifestation, laboratory parameters, imaging features, and tissue biomarkers in a biopsy speci- men. With improved understanding of the natural history and lesion biology, management of GEP-NETs has also evolved. Although surgery remains the only potentially cu- rative therapy for patients with primary GEP-NETs, other available treatments include chemotherapy, interferon, somatostatin analogs, and targeted therapies. Recent im- provements in both morphologic and functional imaging methods have contributed immensely to patient care. Morphologic imaging with contrast agent-enhanced mul- tidetector computed tomography and magnetic resonance imaging is most widely used for initial evaluation and stag- ing of disease in these patients, whereas functional imag- ing techniques are useful both for detection and prognos- tic evaluation and can change treatment planning.