Incidentally discovered, intentionally managed: a narrative review of the last decade’s updates on the management of neuroendocrine tumor of the appendix

Abstract

Appendiceal neuroendocrine neoplasms (aNENs) represent an increasingly recognized and heterogeneous subset of gastroenteropancreatic neuroendocrine tumors (NETs), most often identified incidentally on appendectomy specimens. Postoperative management relies on accurate risk stratification grounded in histopathological assessment and aligned with major international guidelines (WHO, ENETS), which distinguish between well-differentiated NETs (NET grades 1 to 3) and poorly differentiated neuroendocrine carcinomas. Critical prognostic
determinants shaping therapeutic decision-making include tumor size, proliferative index (Ki-67), depth of invasion—particularly mesoappendiceal involvement—and lymphovascular invasion (LVI). Consensus recommendations suggest simple appendectomy as definitive treatment for low-risk tumors (<1 cm) and right hemicolectomy for high-risk lesions (>2 cm) or those exhibiting LVI. However, the management of intermediate-sized aNENs (1.0-2.0 cm) remains the principal area of clinical uncertainty, with emerging data suggesting that appendectomy alone may be sufficient for carefully selected patients without adverse pathological factors. This review synthesizes and critically appraises the most recent evidence and international guidelines with the goal of refining current clinical practice. In particular, it provides an updated framework for individualized risk stratification, evaluates the balance between oncological benefit and procedural morbidity in determining the optimal surgical approach, and outlines evidence-based surveillance strategies to support a more consistent, risk-adapted multidisciplinary management of aNENs.

Keywords Appendiceal neuroendocrine tumor, neuroendocrine neoplasms, surgical management, right hemicolectomy, ENETS guidelines

Ann Gastroenterol 2026; 39 (4): 390-404