Significance of Lymph Node Metastasis in Resectable Well-differentiated Pancreatic Neuroendocrine Tumor

Objectives Understanding the effect of lymph node metastasis (LNM) on prognosis in pancreatic neuroendocrine neoplasm is helpful for surgery and follow-up. In this study, we investigated the significance of LNM in well-differentiated pancreatic neuroendocrine tumors (PanNETs) according to the World Health Organization 2017 classification. Methods We retrospectively collected data for 95 consecutive patients with PanNET who underwent pancreatic resection with curative intent between January 2008 and December 2017 at 6 institutions. The clinicopathological factors were compared in patients with and without LNM, and prognostic factors were analyzed. Results Lymph node metastasis was significantly associated with malignant potential of PanNET, such as larger tumor size, higher Ki-67 index, higher tumor grade, and higher incidence of lymphatic, vessel, and neural invasion. Lymph node metastasis was also associated with disease-free but not overall survival. Multivariate analysis identified NET grade 2 (G2) and G3 as independent risk factors for recurrence after curative resection. Conclusions World Health Organization 2017 classification was the most independent prognostic factor in patients with resectable well-differentiated PanNETs. Patients with G2 and higher-grade tumors require lymph node dissection to improve prognosis.