EP1046 - Ileocolic Mixed Neuroendocrine-Nonneuroendocrine Neoplasm (MiNEN) in a Post-Transplant Patient with Crohn’s Disease: A Case Report Highlighting Diagnostic and Therapeutic Challenges

Purpose/Background: Mixed neuroendocrine-nonneuroendocrine neoplasms (MiNENs) of the gastrointestinal tract are rare epithelial tumors composed of both neuroendocrine and nonneuroendocrine elements, each accounting for at least 30% of the neoplasm. Importantly, these are not hybrid tumors; instead, the two components act independently and may exhibit differing biological aggressiveness and metastatic potential. Therefore, accurate grading and staging of both components are critical for prognosis and treatment planning. Although most frequently reported in the colon and rectum, MiNENs can occur throughout the gastrointestinal tract and are often underrecognized due to their nonspecific clinical manifestations, which can mimic chronic inflammatory conditions

Methods/Interventions: We report a diagnostically challenging case of an ileocolic MiNEN in a 70-year-old male with a history of Crohn's disease, previous ileocolic resection, end-stage renal disease secondary to hypertension, and two deceased-donor kidney transplants. The patient presented in February 2024, approximately six weeks after his most recent transplant, with sepsis and radiographic evidence of small bowel obstruction near a prior ileocolic anastomosis. Conservative management was initially trialed; however, due to inadequate improvement, a laparoscopic converted to open diverting loop ileostomy was required as a temporizing measure to optimize the patient's nutritional status prior to undertaking a more extensive operation. Following several months of nutritional support, the patient underwent exploratory laparotomy, which revealed a fibrotic mass involving multiple small bowel segments with an adjacent abscess cavity near the ileocolic anastomosis. En bloc ileocolic resection with ileostomy reversal was completed.

Results/Outcomes: Although the patient initially tolerated the procedure, he unfortunately expired one month following discharge. Histopathological examination unexpectedly revealed MiNEN with regional nodal involvement.

Conclusion/Discussion: This case highlights the diagnostic challenges of MiNENs in patients with complex gastrointestinal disease. Features such as inflammatory strictures, recurrent abscesses, and adhesions can obscure underlying malignancy and delay recognition. Immunosuppression following organ transplantation adds further complexity to clinical decision-making. Comprehensive histopathological analysis of all resection specimens for presumed obstruction or stricture is essential, especially when presentations are atypical. Although rare, MiNENs should be considered in the differential diagnosis of chronic or recurrent gastrointestinal symptoms in high-risk patients. Given their heterogeneous biology and limited evidence base, management requires individualized strategies and coordinated multidisciplinary care.

Figure A
Intraoperative photograph demonstrating the ileocolic specimen with the instrument tip highlighting the palpable stricture
Figure B
Intraluminal inspection confirming the stricture at the prior anastomosis with the instrument tip positioned along the site of narrowing