Neuroendocrine Tumors of the Gastrointestinal Tract: A Focused Review and Practical Approach for Gastroenterologists

Abstract

Neuroendocrine tumors (NETs) are rare tumors derived from the neuroendocrine cell system, and more commonly found in the gastrointestinal (GI) tract. Over the last decades, the incidence of GI-NETs has been steadily increasing, partly due to the expanding indications for endoscopy. Most patients with NETs are asymptomatic, and their NETs are noticed during screening examinations; thus, endoscopists are on the frontline of the diagnosis of GI-NETs. Since GI-NETs are less frequent than other malignancies, the natural history, diagnosis, and management of these tumors may not be fully understood. In this review, we aim to update the endoscopist on key clinical features and management of patients with gastric, duodenal, and rectal NETs.

Keywords: Endoscopy; Gastrointestinal tract; Neuroendocrine tumors.

Fig. 1

Multiple, small (<1–2 cm), reddish, polypoid lesion in the stomach corpus with surrounding atrophic mucosa suggestive of type I g-NET.

Fig. 2

Single and large (>1 cm) lesion in the stomach corpus with depressed center, consistent with type III g-NET.

Fig. 3

Summarized management of gastric NETs, according to authors' own experience/preference. * The management of type II is similar to type I with the exception that we favor endoscopic resection of all visible tumors; ^† consider ER of NETs with atypical/irregular features; ^# or ESD if depressed/atypical features); NET, neuroendocrine tumor; EMR, endoscopic mucosal resection; ESD, endoscopic submucosal dissection; FTR, full-thickness resection.

Fig. 4

Summarized management of non-functioning duodenal NETs, according to authors' own experience/preference. ^† If periampullary location, surgical resection is recommended regardless of size; endoscopic resection may be performed in very selected cases. NET, neuroendocrine tumor; EMR, endoscopic mucosal resection; ESD, endoscopic submucosal dissection.

Fig. 5

Summarized management of rectal NETs, according to authors' own experience/preference. * ESD, EFTR, or TEMS alternative if no muscular invasion and patient refuses major surgery; ^# anterior resection + total mesorectal excision or abdominoperineal resection; ^† surgery/stent/chemotherapy. EMR, endoscopic mucosal resection; ESD, endoscopic submucosal dissection; EFTR, endoscopic full-thickness resection; TEMS, transanal endoscopic microsurgery.