Due to their increasing incidence, neuroendocrine neoplasms (NENs) are being detected more frequently by endoscopists while they are performing diagnostic upper or lower gastrointestinal (GI) endoscopies. These procedures are usually performed for unrelated indications or for screening, with the tumours often being detected incidentally. The most common scenario is of an endoscopist being surprised by receiving a histology report of a well-differentiated neuroendocrine tumour (NET) after biopsying a small polyp that was initially thought to be benign. This article aims to provide some guidance about what to do next in that situation. All patients with NET should, however, be referred to a fully constituted NEN multidisciplinary team for definitive investigations and management.

In general, the site, size and number of any possible NENs should be fully assessed during the initial endoscopy and representative endoscopic images should be captured. If the initial endoscopic assessment was inadequate, the procedure may need to be repeated. Possible NENs should be sampled using biopsy forceps. Endoscopic resection should only be attempted following histological confirmation of the diagnosis and tumour grade and after additional investigations have been performed to fully stage the tumour and determine its hormone production status. This is essential so that patients do not undergo either unnecessary or inadequate endoscopic resections.

This article discusses the endoscopic features and subsequent assessment of NENs that arise in the stomach, duodenum, terminal ileum and rectum, as these are the common tumour sites within the GI tract.