Neuroendocrine Neoplasms of the Appendix: A Review of the Literature.

Appendiceal neuroendocrine neoplasms (ANENs) comprise rare tumors of the appendix, mainly affecting young populations and characterized by a rather favorable prognosis. The aim of this review was to summarize the current knowledge on these neoplasms, focusing on the management and follow-up of such patients, which still remain under debate. ANENs account for 0.16-2.3% of appendectomies and are usually diagnosed incidentally. The histopathological diagnosis includes the immunohistochemical profile of the tumor in regard to synaptophysin and chromogranin A, as well as the Ki-67 index. The surgical management of ANENs is either simple appendectomy or a more extensive oncological operation including right hemicolectomy. This depends on the stage and the presence of risk factors suggesting a more aggressive disease, such as the exact location, mesoappendiceal or lymphovascular invasion, and the proliferative rate of the tumor. Despite their indolent course, ANENs may relapse. Therefore, lifetime observation is necessary for patients with tumors >2 cm and >1 cm plus additional risk factors; however, more studies should be conducted in order to determine the optimal follow-up strategy.