Optimal lymph node dissection area for pancreatic neuroendocrine neoplasms by tumor location, size, and grade.

Background: Lymph node dissection is required for many pancreatic neuroendocrine neoplasms. However, the need for such dissection has rarely been examined in detail by the tumor size, tumor location, or World Health Organization grading. The objective is to determine which characteristics of pancreatic neuroendocrine neoplasms require lymph node dissection, and to what extent lymph node dissection should be performed.

Methods: A retrospective review was performed of patients who had undergone pancreatectomy with lymph node dissection between 2000 and 2022. Frequency of lymph node metastases stratified by tumor size and grade, and efficacy index (calculated by multiplying the frequency of metastasis to the lymph node station by the 5-year overall survival rate of patients with metastasis to that station) for each lymph node station were evaluated.

Results: Among 130 patients, 29 (22.3%) had lymph node metastases. Tumors larger than 2 cm had a 33.3% lymph node metastasis rate, whereas grade 1 and grade 2 neuroendocrine tumors had rates of 2.4% and 31.8%, respectively. In grade 1 neuroendocrine tumor, for pancreatic head tumor, only peripancreatic head lymph node had an efficacy index of 5.0. Pancreatic body and tail tumor had no lymph node metastases. In grade 2 neuroendocrine tumor, for pancreatic head tumor, peripancreatic and superior mesenteric artery lymph nodes had efficacy indexes of 29.2 and 14.3, respectively. For pancreatic body tumor, peridistal pancreatic lymph node had an efficacy index of 27.3, whereas for pancreatic tail tumor, peridistal pancreatic lymph node and splenic hilum lymph node had an efficacy index of 27.8 and 7.1, respectively.

Conclusion: The optimal extent of lymph node dissection for pancreatic neuroendocrine neoplasms should be determined by considering both the tumor size and grade for each tumor location.