Management of early gastrointestinal neuroendocrine neoplasms

Abstract

Neuroendocrine neoplasms (NENs) of the stomach, duodenum, appendix or rectum that are small (≤ 1 cm) and well differentiated can be considered "early" tumors, since they generally have a (very) good prognosis. In the new WHO classification of 2010, these neoplasms are called neuroendocrine tumors/ carcinoids (NETs), grade (G) 1 or 2, and distinguished from poorly differentiated neuroendocrine carcinomas (NECs), G3. NETs are increasing, with a rise in the age-adjusted incidence in the U.S.A. by about 700 % in the last 35 years. Improved early detection seems to be the main reason for these epidemiological changes. Both the better general availability of endoscopy, and imaging techniques, have led to a shift in the discovery of smaller-sized (≤ 10-20 mm) intestinal NETs/carcinoids and earlier tumor stages at diagnosis. Endoscopic screening is therefore effective in the early diagnosis, not only of colorectal adenocarcinomas, but also of NETs/carcinoids. Endoscopic removal, followed up with endoscopic surveillance is the treatment of choice in NETs/carcinoids of the stomach, duodenum and rectum that are ≤ 10 mm in size, have a low proliferative activity (G1), do not infiltrate the muscular layer and show no angioinvasion. In all the other intestinal NENs, optimal treatment generally needs surgery and/or medical therapy depending on type, biology and stage of the tumor, as well as the individual situation of the patient.

Keywords: Appendix; Carcinoid; Duodenum; Gut; Neuroendocrine tumor; Prognosis; Rectum; Small size; Stomach; Treatment.

Figure 1

Endoscopic images of early gastrointestinal NETs/carcinoids. A: Multiple small (< 1 cm), well differentiated (G1) type 2 gastric NETs/carcinoids associated with Zollinger-Ellison-syndrome (ZES) and multiple endocrine neoplasia type 1 (MEN1); B: Multiple small (< 1 cm), well differentiated (G1) type 1 gastric NETs/carcinoids associated with autoimmune chronic atrophic gastritis and pernicious anemia; C: 8 mm measuring NET/carcinoid in the duodenal bulb (C1). Endoscopic ultrasound shows the infiltration of mucosa and submucosa (C2). The duodenal NET/carcinoid exhibits a low echogenic pattern on EUS; D: 10 mm measuring NET/carcinoid of the rectum (D1). 7 mm measuring NET/carcinoid of the rectum (D2). Modified from reference[13-15]. NETs: neuroendocrine tumors; EUS: Endoscopic ultrasound.