Unifocal versus Multiple Ileal Neuroendocrine Tumors Location: An Embryological Origin

Abstract

<b><i>Introduction:</i></b> Small-intestinal neuroendocrine tumors (SI-NET) are situated preferentially within the ileum. The aim was to describe a potential difference in location between unifocal and multiple ileal-NET. <b><i>Patients and Methods:</i></b> Between December 2010 and December 2019, all consecutive patients who underwent resection in our European Neuroendocrine Tumor Society Center of Excellence, of at least 1 non-duodenal SI-NET, were retrospectively included. The main objective was to prove that multiple ileal-NET were mostly located on the left side of the superior mesenteric artery (SMA) axis (defined as 40 cm from the ileocecal valve), and unifocal ones on the right side. <b><i>Results:</i></b> Ninety-four patients were included, 6 with unifocal jejunal-NET located 35 cm (range, 10–60) from the duodenojejunal angle (DJA), 44 (47%) with unifocal ileal-NET and 44 (47%) with multiple ileal-NET. The median number of tumors in multiple ileal-NET was 7 (range, 2–95), within a median small bowel segment of 105 cm (10–240). The median length between the proximal tumor and the DJA was 428 cm (300–635) and 540 cm (350–725) for the distal one; 40 (91%) of them were located on the left side of the SMA axis. In contrast, unifocal ileal-NET were located at a median distance of 577 cm (305–820) from the DJA (<i>p</i> &#x3c; 0.001, compared to multiple ileal-NET); 30 (68%) of them were on the right side of the SMA axis (<i>p</i> &#x3c; 0.001). <b><i>Conclusion:</i></b> Multiple ileal-NET are mostly located on the left side of the SMA axis. Further studies are warranted to explore the embryological origin of unifocal versus multiple ileal-NET.