Neuroendocrine tumours (NETs) are relatively uncommon tumours of the gut previously described formerly thought to arise from the neural crest, but most are now thought to arise from neuroendocrine cells of the gut directly. Tumours arising from the gut are principally pancreatic islet cell tumours, pNETS, and midgut tumours, but more frequently rectal carcinoids in the Far East. The pNETs are usually non-functioning but may secrete a variety of hormones giving rise to secretory syndromes as gastrinomas, glucagonomas etc. Secretory syndromes can be dealt with in terms of the specific syndrome, eg, using diazoxide for insulinomas or PPIs for gastrinomas, but somatostatin analogues such as octreotide or lanreotide are usually effective, and recent data suggest they may retard tumour growth. For both pNETs and the midgut carcinoids loco-regional approaches to liver disease are often very useful, while for progressive disease chemotherapy may be effective in slowing progression, especially temozolomide and capecitabine. In addition, radionuclide therapy with ⁹⁰Y-octreotide or ¹⁷⁷Lu-octreotate show considerable promise. However, two recent multicentre randomised trials have shown that both the tyrosine kinase inhibitor sunitinib, and the mTOR inhibitor everolimus, can significantly improve progression free survival, and there are encouraging data for bevacizumab.

For the midgut carcinoids, some 20-30% will exhibit the carcinoid syndrome associated with elevated urinary 5HIAA excretion, and this is usually alleviated by long-acting somatostatin analogues; there is also evidence that these agents may improve progression free survival. Vitamin B complex should be given to maintain niacin levels. For patients with symptoms resistant to these analogues, either initially or on progression, recent data have suggested that 5HT synthesis inhibitors may play a role. Carcinoid heart disease may require surgical repair. For progressive disease, recent data suggest an increase in progression free survival with everolimus.

In general, these complex tumours warrant assessment by a multidisciplinary group in a centre of excellence where the expertise, skill-mix and technology are readily available.