Clinical Relevance of High-Grade Pancreatic Intraepithelial Neoplasia at the Pancreatic Transection Margin in Patients with Pancreatic Ductal Adenocarcinoma.

Background: The clinical relevance of high-grade pancreatic intraepithelial neoplasia (PanIN) at the pancreatic transection margin (PTM) during resection of pancreatic ductal adenocarcinoma (PDAC) remains unclear.

Methods: A total of 358 patients who underwent R0 resection for PDAC between January 2010 and December 2022 were included. The permanent sections used for the intraoperative frozen section diagnosis of PTM were evaluated for the PanIN grade.

Results: Among 358 patients, 35 patients had low-grade PanIN (9.8%), and 17 had high-grade PanIN (4.7%) at the PTM. The 2-year overall survival (OS), disease-free survival (DSS), and relapse-free survival (RFS) did not differ markedly among patients with normal epithelium, low-grade PanIN, or high-grade PanIN at the margin. As the clinical features differed between patients with high-grade PanIN at the PTM and those without, we adjusted the patients' background factors using propensity score matching. The 2-year OS, DSS, and RFS rates were not significantly different between the groups. In addition, we investigated the details of 17 cases of high-grade PanIN in the PTM. The analysis revealed that 11 patients experienced recurrence after surgery. Among them, two cases of T1N0 showed recurrence in the remnant pancreas more than 2 years after surgery, while nine cases exhibited recurrence outside the remnant pancreas, such as the liver and lungs, within 2 years.

Conclusions: Patients with high-grade PanIN at the PTM did not show a significantly different prognosis than those without; however, recurrence in the remnant pancreas was observed in long-term survivors. Therefore, rigorous long-term follow-up is essential for such patients.