Tumour detection in syndromic NET (carcinoid syndrome)

Many gastro-enteropancreatic neuroendocrine tumours (GEP-NETs) secrete biologically active substances and can present with distinct clinical syndromes related to their oversecretion. In particular, carcinoid syndrome (CS) is a compendium of clinical manifestations including secretory diarrhoea, flushing and less commonly wheezing and dyspnoea secondary to overproduction of such compounds, mainly serotonin. Carcinoid syndrome is almost exclusively derived from small intestinal NETs that have metastasized to the liver and may also be associated with extensive fibrosis of heart valves and the mesenterium. Although the diagnosis is usually delayed due to the lack of tumour-specific symptoms, measurement of specific tumour metabolites such as 5-hydroxyindoloacetic acid facilitates the diagnosis. Conventional radiology and functioning imaging modalities using specific and occasionally non-specific tracers are used to identify the extent of disease and also provide information regarding prognosis and the application of specific treatment. The development though of diagnostic and predictive biomarkers that would allow for individualized workup and selection of specific treatments remains a priority in the field