[Gastroenteropancreatic endocrine tumors]

Gastroenteropancreatic neuroendocrine tumors (GEP-NET) are a rare, heterogeneous group of neoplasms. Only 2% of gastrointestinal tumors belong to the group of neuroendocrine neoplasms.

A wide spectrum of diagnostic imaging modalities is available: apart from ultrasound not only computed tomography (CT) but also magnetic resonance imaging (MRI) and positron emission tomography CT (PET-CT) play an important role in detection and staging of GEP-NETs.

The PET-CT technique with somatostatin analogues is used for staging as well as for evaluation and monitoring of treatment with peptide radionuclide radiation therapy.

According to the literature NETs of the small bowel with a size over 3 cm can be detected with a sensitivity of 84.7% and a specificity of 96.6% using CT enteroclysis and MR enteroclysis provides the detection of NETs of the small bowel in 93.3% of cases. 'The sensitivity of MRI in detection of pancreatic NETs is between 74% and 100% and is, therefore, higher than CT. Detection of small primary tumors is carried out using PET-CT and seems to be the most sensitive imaging modality to identify the exact location. On the other hand MRI has to be regarded as the best imaging modality for detection of liver metastases compared to CT and PET-CT.

The role of diagnostic imaging is to identify the exact location of the primary tumor and possible metastases, to define an appropriate therapy and to monitor treatment effects; however, the choice of the most appropriate diagnostic imaging modality varies depending on the location and type of the primary tumor.

The GEP-NETs are predominantly well-vascularized; therefore, dual-phase CT/MR imaging with the arterial and venous phases after contrast media injection is mandatory for detection and localization of primary tumors and metastases. For whole body staging CT and PET-CT should be performed.