MODERN APPROACHES AND RECENT ADVANCES IN NEUROENDOCRINE TUMORS

Modern Approaches and Recent Advances in Neuroendocrine Tumors-kapak

GENERAL CHARACTERISTICS AND MANAGEMENT OF APPENDIX NEUROENDOCRINE TUMORS

Adem Şentürk1 Recayi Çapoğlu2

1Sakarya University Training and Research Hospital, Department of Surgical Oncology, Sakarya, Türkiye
2Sakarya University Training and Research Hospital, Department of General Surgery, Sakarya, Türkiye

Şentürk A, Çapoğlu R. General Characteristics and Management of Appendix Neuroendocrine Tumors. In: Gönüllü E, Karaman K, editors. Modern Approaches and Recent Advances in Neuroendocrine Tumors. 1st ed. Ankara: Türkiye Klinikleri; 2025. p.153-162.

ABSTRACT

Appendiceal neuroendocrine tumors (NETs) are rare neoplasms typically discovered incidentally on pathological examination of appendectomy specimens. These tumors represent 0.5-1% of all gastrointestinal neoplasms and are slightly more common in women, typically detected between 20 and 50 years of age. They are most frequently located at the distal tip of the appendix; those larger than 2 cm or located at the base carry a higher risk of lymph node and distant metastasis. Appendiceal NETs are categorized as well-differentiated (G1, G2, G3) or poorly differentiated (NEC, usually G3). Well-differentiated G3 NETs have a worse prognosis than G1-G2 but fare better than NECs. Goblet cell carcinoid is currently reclassified as goblet cell adenocarcinoma or mixed neuroendocrine neoplasm (MiNEN) in contemporary guidelines. Most patients are asymptomatic, and the tumor is incidentally diagnosed in specimens removed for acute appendicitis or nonspecific abdominal pain. Larger or basally located lesions may obstruct the lumen, causing appendicitis. Carcinoid syndrome (flushing, diarrhea, etc.) is rare in appendiceal NETs, occurring in <1% of cases, typically when hepatic metastases are present. Diagnosis is typically established postoperatively via pathological analysis. Risk assessment includes tumor size, depth of mesoappendiceal invasion (>3 mm), lymphovascular invasion, surgical margin status, and tumor grade (Ki-67, mitotic count). Additional imaging (CT/MR, Ga-68 DOTATATE PET/ CT, or 18F-FDG PET/CT) and biochemical markers (Chromogranin A, 5-HIAA) may be used based on the risk profile. For well-differentiated NETs smaller than 1 cm, appendectomy alone is sufficient. Tumors larger than 2 cm or those exhibiting high-risk features warrant additional surgery, typically right hemicolectomy. In metastatic or high-risk disease, therapeutic options include somatostatin analogs, chemotherapy, and targeted agents (mTOR inhibitors, tyrosine kinase inhibitors). Follow-up strategies differ by tumor size and histological features; low-risk cases do not require extensive imaging or prolonged surveillance, whereas high-risk or metastatic patients benefit from closer multidisciplinary monitoring. Appendiceal NETs are often diagnosed incidentally and usually have low aggressiveness. Management is guided by tumor size, location, and histopathological risk factors. Early recognition and appropriate surgical intervention ensure an excellent prognosis in most cases, but advanced or metastatic presentations necessitate a multidisciplinary approach and more complex treatments.

Keywords: Appendix; Neuroendocrine tumor; Carcinoid syndrome; Surgical management; Somatostatin analogs; Metastatic NET

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