Low-Grade Appendiceal Mucinous Neoplasm Presenting as Small Intestine Obstruction Due to Internal Hernia: A Case Report.

Background: Appendiceal mucinous neoplasms (AMNs) are rare tumors that are often discovered incidentally and may present with non-specific symptoms such as abdominal pain, ascites, or features mimicking appendicitis. Case Presentation: A 72-year-old male presented with small intestine obstruction secondary to an internal hernia. CT scan imaging initially suggested adhesive bands; however, surgical exploration revealed an inflamed, tumor-bearing appendix tip adherent to the mesentery, forming a hernia orifice that trapped a loop of small intestine. The patient underwent appendectomy, mesenteric mass resection, and hernia repair. Histopathology confirmed a low-grade appendiceal mucinous neoplasm (LAMN) with mucinous invasion of the mesentery, explaining the mass formation and mechanism of herniation. Conclusion: This case illustrates that a locally invasive LAMN, even in the absence of peritoneal dissemination, can act as a lead point for an internal hernia and should be considered in the differential diagnosis of bowel obstruction and internal hernia, particularly in elderly patients.