Bérénice Rault-Petit, Christine Do Cao, Serge Guyétant, Rosine Guimbaud, Vincent Rohmer, Catherine Julié, Eric Baudin, Bernard Goichot, Romain Coriat, Antoine Tabarin, Jeanne Ramos, Pierre Goudet, Valérie Hervieu, Jean-Yves Scoazec, Thomas Walter

The primary endpoint was to analyze the predictive factors of lymph node involvement (LN+). Indications for additional right hemicolectomy (RHC) with lymph node (LN) resection after appendectomy for appendix neuroendocrine tumor (A-NET) remain controversial, especially for tumors between 1 and 2 cm in size. National study including all patients with nonmetastatic A-NET diagnosed after January, 2010 in France. In all, 403 patients were included. A-NETs were: within tip (67%), body (24%) or base (9%) of the appendix; tumor size was < 1 cm (62%), 1 to 2 cm (30%), or >2 cm (8%); grade 1 (91%); mesoappendix involvement 3 mm (5%); lymphovascular (15%) or perineural (24%) invasion; and positive resection margin (8%). According to the European NeuroEndocrine Tumor Society (ENETS) recommendations, 85 patients (21%) should have undergone RHC. The agreement between ENETS guidelines and the multidisciplinary tumor board for complementary RHC was 89%. In all, 100 (25%) patients underwent RHC with LN resection, 26 of whom had LN+. Tumor size (best cut-off at 1.95 cm), lymphovascular and perineural invasion, and pT classifications were associated with LN+. Among the 44 patients who underwent RHC for a tumor of 1 to 2 cm in size, 8 (18%) had LN+. No predictive factor of LN+ (base, resection margins, grade, mesoappendix, lymphovascular, perineural involvement) was found in this subgroup of patients. In the largest study using the latest pathological criteria for completion RHC in A-NET, a quarter of patients had residual tumor. Further studies are warranted to demonstrate the survival impact of RHC in this setting.