Supplementary Material for: Evaluation of the Site and Frequency of Lymph Node Metastasis with Non-Functioning Pancreatic Neuroendocrine Tumor

Backgrounds: The optimal lymph node dissection range in patients with non-functioning pancreatic neuroendocrine tumors is not yet clear. In this study, we investigated the site and frequency of lymph node metastasis and the significance of lymph node dissection in patients with non-functioning pancreatic neuroendocrine tumors. Methods: This retrospective study analyzed 74 patients who underwent a curative pancreatectomy for non-functioning pancreatic neuroendocrine tumors between 2000 and 2016. The site and frequency of lymph node metastasis and clinicopathological factors were evaluated. Results: The rate of synchronous lymph node metastasis was 17.6%, with 11.1 and 29.4% for tumors with diameters of 10–19 mm and ≥20 mm, respectively. Lymph node metastasis was not observed for tumors with a diameter <10 mm. Lymph node metastasis was observed along the anterior (17a: 13.3%, 17b: 12.5%) and posterior (13a: 5.9%, 13b: 26.7%) surfaces of the pancreatic head and the superior mesenteric artery (14p: 12.5%, 14d: 7.7%) in patients with non-functioning pancreatic head neuroendocrine tumors, in the common hepatic (8a: 5.3%), splenic (10: 14.3%, 11p: 17.6%, 11d: 12.5%), and super mesenteric artery (14d: 14.3%) in patients with non-functioning pancreatic body neuroendocrine tumors, and only in the splenic artery (11p: 8.3%, 11d: 7.7%) in patients with non-functioning pancreatic tail neuroendocrine tumors. Grade 2 (HR = 6.21) and synchronous lymph node metastasis (HR = 10.4) were significant risk factors for disease-free survival. The 5-year disease-free survival was 95.7, 72.6, and 0% in patients with 0, 1, and 2 prognostic factors, respectively. Conclusions: This study clarified the site and frequency of lymph node metastasis and the optimal range of lymph node dissection in patients with non-functioning pancreatic neuroendocrine tumors.