EP663 - Incidentally Identified Appendiceal Neuroendocrine Tumors in Patients with Crohn’s Disease: A Case Series and Review of the Literature

Purpose/Background: Appendiceal neuroendocrine tumors (aNETs) are rare neoplasms, accounting for less than 1% of gastrointestinal malignancies. They are thought to arise from neuroendocrine cells of the appendiceal wall and are typically diagnosed incidentally following bowel resection or appendectomy for suspected acute appendicitis. Emerging evidence suggests that patients with Crohn's disease (CD) may have a higher prevalence of aNETs when compared with the general population.

Methods/Interventions: We report two cases of patients with Crohn's disease who were incidentally found to have low-grade aNETs following bowel resection for indications related to CD. Case 1 is a 43-year-old female with recently diagnosed fistulizing CD who underwent a laparoscopic right hemicolectomy and fistula takedown for entero-colonic and entero-vesical fistulas. Final pathology was notable for a 0.6 cm well-differentiated neuroendocrine tumor of the distal appendix, grade 1, which extended into the muscularis propria, without lymphovascular invasion (pT1N0). Case 2 is a 54-year-old female who presented for evaluation following multiple admissions for small bowel obstructions secondary to stricturing CD. She was first diagnosed with CD at the age of 30 and was presently managed with Vedolizumab. Following clinical discussion, she underwent a laparoscopic ileocolic resection with primary anastomosis and had an uncomplicated postoperative course. Pathology revealed a 1.3 cm well-differentiated neuroendocrine tumor, grade 1, involving the distal tip of the appendix with invasion into subserosal tissue and periappendiceal fat, without lymphovascular invasion (pT3N0).

Results/Outcomes: Case 1 (pT1N0) did not require additional surveillance based on established NCCN guidelines and ultimately transferred her care to another facility following a long-distance relocation. Case 2 (pT3N0) established care with medical oncology and has continued routine surveillance, with no clinical or radiographic evidence of recurrence to date.

Conclusion/Discussion: These cases support existing data that Crohn's disease may be associated with an increased risk of aNETs, possibly related to chronic inflammation, immune system modulation, or as a result of detection bias due to frequent surgical intervention in this population. Management principles based on current guidelines include appendectomy alone for tumors < 1 cm in the absence of high-risk features, while larger or higher-risk lesions may require formal right hemicolectomy with postoperative surveillance. Careful histopathologic review of resection specimens in Crohn's disease is essential. Larger studies are needed to clarify prevalence, mechanisms, and optimal management strategies for aNETs in this patient population.

Intraoperative Photo from Case 1
Right hemicolectomy specimen with instrument tunneling through entero-colonic fistula.
Intraoperative Photo from Case 2
Ileocolic specimen with signs of chronic inflammatory changes along a several centimeter segment of distal ileum, including hyperemia and creeping fat.