Liver Margin Positivity Emerges as a Major Determinant of R1 Resection in Perihilar Cholangiocarcinoma : Ann Surg | May 2026

Introduction

Perihilar Cholangiocarcinoma remains one of the most technically challenging hepatobiliary malignancies to treat surgically. Achieving an R0 resection is critical because microscopic residual disease strongly influences recurrence and long-term survival. While ductal margins are routinely assessed, the significance and optimal evaluation of the liver margin have remained poorly defined despite it representing the largest surgical margin in major hepatectomy specimens.

Problem Statement

The prevalence, spatial distribution and clinical relevance of positive liver margins in resected perihilar cholangiocarcinoma are incompletely understood, and standardized pathological assessment strategies for liver margins are lacking.

Summary

This multicenter study investigated the status of liver margins in resected perihilar cholangiocarcinoma using serial whole-mount digital large-section analysis, providing important new insights into patterns of microscopic residual disease and margin assessment methodology.

The study demonstrated that liver margin positivity is substantially underrecognized using conventional small-section pathology techniques. When assessed using whole-mount digital large sections, the liver margin R1 rate approached 39%, compared with only 6% using conventional small-section evaluation alone. This striking discrepancy highlights the limitations of traditional sampling approaches in accurately characterizing microscopic residual disease within the liver transection plane.

Importantly, patients classified as R0 in the discovery cohort undergoing more comprehensive liver margin assessment experienced superior overall survival and recurrence-free survival, emphasizing the major prognostic implications of accurate margin characterization.

A particularly notable finding was the spatial clustering of microscopic carcinoma near the proximal ductal margin. Approximately 95% of carcinoma involvement within the liver margin was located within 20 mm of the proximal ductal margin, suggesting a biologically and surgically meaningful zone of highest residual disease risk.

The investigators further identified a proximal ductal margin distance below 5 mm as an independent predictor of liver margin positivity. Patients with narrow proximal ductal clearance were significantly more likely to harbor occult liver margin involvement, reinforcing the interconnected anatomy of ductal and parenchymal spread in perihilar cholangiocarcinoma.

Clinically, the study has important implications for both surgery and pathology workflows. The findings suggest that current routine pathology approaches may significantly underestimate true R1 rates in perihilar cholangiocarcinoma, potentially leading to inaccurate prognostication and postoperative treatment planning.

The proposed examination strategy focusing on a 20 mm radius around the proximal ductal margin provides a practical framework for standardized liver margin assessment. This targeted approach may improve diagnostic yield while remaining operationally feasible within routine pathology practice.

From a biological perspective, the work also illustrates the infiltrative growth characteristics of perihilar cholangiocarcinoma. Microscopic extension beyond visibly apparent tumor boundaries into adjacent hepatic parenchyma may partly explain the persistently high recurrence rates observed even after apparently curative surgery.

The study additionally highlights the growing role of digital pathology and whole-mount sectioning in hepatobiliary oncology. Advanced pathological mapping techniques may increasingly refine understanding of tumor spread patterns and improve surgical margin interpretation.

These findings may also influence operative strategy. Awareness that narrow proximal ductal margins strongly correlate with occult liver margin involvement could affect intraoperative decision-making regarding extent of resection and frozen-section interpretation.

Importantly, the work raises broader questions regarding the definition of true oncologic radicality in perihilar cholangiocarcinoma. Conventional binary R0/R1 classification may not fully capture the complexity of microscopic parenchymal extension patterns in this disease.

Overall, this multicenter study identifies liver margin positivity as a major and previously underappreciated contributor to R1 resection in perihilar cholangiocarcinoma. Whole-mount digital large-section pathology substantially improves detection of occult residual disease and supports a standardized focused assessment strategy centered around the proximal ductal margin region.