Appendiceal Neuroendocrine Neoplasms: an Update for 2023

To summarize the literature from the last 5 years on treatment of appendiceal neuroendocrine neoplasms (aNEN). Furthermore, to evaluate the prognostic significance of lymph node metastases, indications for adjuvant treatment, and challenges of the current follow-up regimen.

Simple appendectomy is sufficient in tumors < 1 cm while extended surgery is indicated in tumors > 2 cm. In a multicenter study of aNENs measuring 1–2 cm, extended surgery offered no significant prognostic advantage and is now limited to incomplete tumor resection or high-grade G2 or G3 aNEN. Follow-up remains debatable, as the use of imaging and biomarkers lacks validation.

While surgical procedure is well established in aNEN tumors < 1 cm and > 2 cm, the need for extended surgery in aNEN tumors 1–2 cm is questionable. Future studies should address the prognostic impact of lymph node metastases and the optimal design and duration of follow-up.