Appendiceal neuroendocrine tumors in children and adolescents: The European Cooperative Study Group for Pediatric Rare Tumors (EXPeRT) diagnostic and therapeutic recommendations.

Neuroendocrine tumors of the appendix, formerly known as carcinoid tumors, represent a rare entity. They are slow-growing tumors, characterized by an indolent clinical course. In pediatric patients, the 5-year overall survival is estimated to be 100% and the event-free survival slightly less than 100%, with only one reported case of local relapse to date. Nevertheless, a proportion of these patients still undergo a second surgery, mostly represented by right hemicolectomy with mesenteric lymphadenectomy, in consideration of the presence of certain risk factors (size >1.5 or 2 cm; tumors of the appendiceal base with or without suspicious residuals, mesoappendiceal invasion, lymphovascular invasion, serosal breach). This approach represents an overtreatment of patients with a benign clinical course regardless of the presence of risk factors and/or whether a second surgery is performed. National recommendations for diagnosis, treatment, and follow-up of neuroendocrine tumors of the appendix in pediatric age are available in France, Italy, and Germany, but international consensus is lacking. This review presents the internationally harmonized recommendations for the diagnosis and treatment of neuroendocrine tumors of the appendix in children and adolescents, established by the European Cooperative Study Group for Pediatric Rare Tumors group.