CT/MRI of neuroendocrine tumours.

Neuroendocrine tumours (NETs) are often thought to be rare and rather recherché cancers which are of little concern to the general physician, surgeon or radiologist because of their rarity and esoteric nature. In fact, while relatively uncommon, the total group of gastro-entero-pancreatic (GEP) tumours incorporates the spectrum of all types of carcinoids, including bronchial carcinoids, and the whole gamut of islet-cell tumours. Some of these may present as functioning tumours, with a plethora of hormonal secretions and concomitant clinical syndromes, and GEPs in general have an incidence around 30 per million population per year. This means that in the whole European Union, for example, there will be in the region of 12,000 new patients every year presenting with one or another manifestation of these tumours. Furthermore, the comparatively long survival of many of these patients, compared to more common adenocarcinomas or epithelial tumours, implies that the point prevalence is also not inconsiderable. However, it is undoubtedly true that these tumours can be difficult to identify, especially in their early stages, and it is then that radiological investigation becomes of paramount importance. Having taken into account all these considerations, most investigators would initiate investigation of a suspected or biochemically proven islet-cell tumour with cross-sectional imaging-either CT or MRI. This will clearly identify the larger lesions, allow assessment of the entire abdomen, and provide valuable information on the presence of hepatic metastates.