The Distal Predilection of Small Bowel Neuroendocrine Tumors.

Abstract

The small bowel (SB) is the most common site of neuroendocrine tumors (NETs) of the GI tract. These are described as being predominantly jejunoileal, but their exact locations within the SB have not been well defined. We sought to determine prospectively the spectrum of SBNET locations. Patients undergoing exploration for SBNET primaries had measurement of bowel length, tumor locations, and resection length recorded. Correlations of clinicopathologic factors were performed, and analysis done utilizing Welch's t test, Chi square test, and the Kaplan-Meier method. Measurements were recorded in 123 patients, 107 of whom had complete information. Multifocal tumors (MTs) were found in 69 (56%) and unifocal (UTs) in 54 (44%) patients. Only 1of 107 patients had a tumor within 100cm of the ligament of Treitz (LT), whereas 77 of 107 (72%) had tumors within 100cm of the ileocecal valve (ICV). No MTs were found within 100cm of LT, whereas 41 of 60 (68%) patients had all (10) or at least one tumor (31) located within 100cm of the ICV. MTs required a mean resection length of 108 versus 59cm for UTs (p < 0.01). Seventy-seven percent of UTs (36/47) were within 100cm of ICV. Tumors occurring only between > 100cm from the LT and ICV were seen in 29 of 107 (27%) patients. SBNETs are frequently multifocal and most commonly located within 100cm of the ICV. SBNETs are less prevalent proximally in the small bowel, which may result from anatomic differences in enterochromaffin cell density, hormonal factors, or environmental exposures in the distal SB.