Unmet needs in appendiceal neuroendocrine neoplasms

Appendiceal neuroendocrine neoplasms (ANEN) are mostly discovered coincidentally during appendicectomy and usually have a benign clinical course; thus, appendicectomy alone is considered curative. However, in some cases, a malignant potential is suspected, and therefore additional operations such as completion right hemicolectomy are considered. The existing European Neuroendocrine Tumour Society (ENETS) guidelines provide useful data about epidemiology and prognosis, as well as practical recommendations with regards to the risk factors for a more aggressive disease course and the indications for a secondary operation. However, these guidelines are based on heterogeneous and retrospective studies. Therefore, the evidence does not seem to be robust, and there are still unmet needs in terms of accurate epidemiology and overall prognosis, optimal diagnostic and follow-up strategy, as well as identified risk factors that would indicate a more aggressive surgical approach at the beginning and a more intense follow-up. In this review, we are adopting a critical approach of the ENETS guidelines and published series for ANEN, focusing on the above-noted "grey areas".