Optimal Lymph Node Dissection Area for Pancreatic Neuroendocrine Neoplasms by Tumor Location, Size, and Grade

Lymph node (LN) dissection is required for many pancreatic neuroendocrine neoplasms (Pan-NENs). However, the need for such dissection has rarely been examined in detail by the tumor size, tumor location or WHO grading. The objective is to determine which characteristics of Pan-NENs require LN dissection, and to what extent LN dissection should be performed. Retrospective review of patients who had undergone pancreatectomy with LN dissection between 2000 and 2022 were analyzed. Frequency of LN metastases stratified by tumor size and grade, and Efficacy index (calculated by multiplying the frequency of metastasis to the LN station by the 5-year overall survival rate of patients with metastasis to that station) for each LN station were evaluated. Among 130 patients, 29 (22.3%) had LN metastases. Tumors larger than 2 cm had a 33.3% LN metastasis rate, while NET-G1 had a 2.4% and NET-G2 had a 31.8%, respectively. In NET-G1, for pancreatic head tumor, only peri-pancreatic head LN had an efficacy index of 5.0. Pancreatic body and tail tumor had no LN metastases. In NET-G2, for pancreatic head tumor, peri-pancreatic LN and SMA LN had efficacy index of 29.2 and 14.3, respectively. For pancreatic body tumor, peri-distal pancreatic LN had efficacy index of 27.3, while for pancreatic tail tumor, peri-distal pancreatic LN and splenic hilum LN had efficacy index of 27.8 and 7.1, respectively. The optimal extent of LN dissection for Pan-NENs should be determined by considering both the tumor size and grade for each tumor location.