Ileal neuroendocrine tumors detected during screening or diagnostic colonoscopy – case series and comparison of tumor characteristics.

Abstract Purpose: Small intestinal neuroendocrine tumors are the most common type of small bowel malignancy observed. Ileal tumors are often found in patients undergoing ileal intubation during colonoscopy. Our aim was to compare ileal neuroendocrine tumor characteristics when discovered during screening versus diagnostic colonoscopy. Methods: We reviewed all ileal neuroendocrine tumor cases from 2005-2021. We recorded patient age, gender, colonoscopy indication at diagnosis, timing of prior colonoscopy (if ever performed) and whether ileal intubation was performed, tumor size and stage after resection, and disease-free survival. Results: Twenty-eight ileal neuroendocrine tumor cases were diagnosed at colonoscopy. Fifteen patients were having initial screening or surveillance. The remaining 13 were having diagnostic evaluation of symptoms, abnormal CT imaging, or abnormal stool test results. A prior colonoscopy was performed within the preceding 10-year period in 14 cases, and of these, 8 did not include terminal ileum intubation. Tumor size ranged from 0.5 to 3.7 cm and mean size was nearly identical in screening and diagnostic groups (1.7 vs 1.9 cm). Lymph nodes were involved in 25 of 28 patients. At diagnosis, 2 patients had distant metastases. Mean survival-to-date was similar for both groups as well (85 vs 88 months). Conclusion: Nearly all ileal neuroendocrine tumors discovered during colonoscopy were associated with nodal metastasis at the time of diagnosis. Most, however, have enjoyed prolonged survival. No significant difference in tumor size, stage, or survival was observed between patients having screening versus diagnostic colonoscopy. Our findings support performing routine ileal intubation during colonoscopy for all indications.