The Inverted Appendix ‐ A Potentially Problematic Diagnosis: Clinicopathologic Analysis of 21 Cases

Abstract

Aims

Inverted appendices are rare but have the potential to cause diagnostic confusion among endoscopists and pathologists. The aim of this study was to describe the clinicopathologic features of inverted appendices seen at our institution over the last 30 years.

Methods and Results

21 inverted appendices were identified and the clinical and pathologic features reviewed. Patients were predominantly middle aged women. Most cases were detected incidentally on colonoscopy. Endoscopically, inverted appendices appeared polypoid in the proximal cecum. All resections featured associated pathologic processes, including endometriosis (n = 3), inflammatory mucocele (n = 1), low grade appendiceal mucinous neoplasm (n = 2), traditional serrated adenoma (n = 1), and inflammatory fibroid polyp (n = 1). Five cases were endoscopically mischaracterized as cecal polyps and removed via polypectomy; initial pathologic impressions were erroneous in most cases. All polypectomies featured a dome‐like configuration covered by mucosa on the convex surface; the majority had aggregates of ganglion cells and neural plexi embedded in muscularis propria. The vast majority of cases, regardless of the procedure, showed lymphoid aggregates. Among post‐polypectomy patients with follow up, none experienced perforation‐associated morbidity despite histologic presence of muscularis propria.

Conclusions

The diagnosis of an inverted appendix should be considered in polypectomy specimens from the cecum or appendiceal orificewith p 1) dome‐like tissue configuration covered by mucosa on the convex surface, 2) a deep, robust smooth muscle component with ganglion cells (muscularis propria), and 3) associated lymphoid aggregates. Prompt recognition on H&E will avoid unnecessary time and resource investment.

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