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 manifestations. All NETs are potentially malignant but differ in their biologic characteristics and the probability of metastatic disease. The pathologic classification of these tumors relies on their proliferation and differentiation. In the past decades, several nomenclatures have been proposed to stratify neuroendocrine tumors, but the World Health Organization classification is the one that is most widely accepted and used. The diagnosis of neuroendocrine tumor relies on clinical manifestation, laboratory parameters, imaging features, and tissue biomarkers in a biopsy specimen. With improved understanding of the natural history and lesion biology, management of GEP-NETs has also evolved. Although surgery remains the only potentially curative therapy for patients with primary GEP-NETs, other available treatments include chemotherapy, interferon, somatostatin analogs, and targeted therapies. Recent improvements in both morphologic and functional imaging methods have contributed immensely to patient care. Morphologic imaging with contrast agent-enhanced multidetector computed tomography and magnetic resonance imaging is most widely used for initial evaluation and staging of disease in these patients, whereas functional imaging techniques are useful both for detection and prognostic evaluation and can change treatment planning.

Fused positron emission tomography (PET)/computed tomography (CT) is a recently developed technology that couples the functional information of PET with the anatomic details of CT. Integrated PET/CT scanners produce both PET and contrast material-enhanced CT images of the entire body in one setting. Typically, the amount of fluorine 18 (18F) fluorodeoxyglucose (FDG) uptake in normal pancreatic parenchyma is insignificant compared with that of the liver. However, both malignant (eg, adenocarcinoma) and benign (eg, acute pancreatitis) pancreatic conditions may demonstrate intense FDG uptake. PET/CT provides an opportunity to depict pancreatic tumors and distant metastases, perform preoperative staging, and monitor response to treatment, and it has proved useful in distinguishing postoperative fibrosis from recurrence. In selected cases, PET/CT findings may be used to help diagnose autoimmune pancreatitis mimicking a mass by depicting systemic involvement. PET/CT may also be used to direct biopsy to sites more likely to yield representative tumor tissue. Novel radiolabeled molecules, such as sigma-receptor ligands and 18F-3'-fluoro-3'-deoxy-l-thymidine (FLT), may play an even greater role in distinguishing tumor recurrence from postoperative fibrosis or inflammation.

A diagnostic algorithm including diffusion-weighted MRI criteria may help even inexperienced readers distinguish uterine sarcoma from atypical leiomyoma. Background Improving the differentiation of uterine sarcomas from atypical leiomyomas remains a clinical challenge and is needed to avoid inappropriate surgery. Purpose To develop a diagnostic algo...