13 Interobserver Agreement in Measuring Submucosal Invasion Depth in pT1b Esophageal Squamous Cell Carcinoma: Practical Implications for Post-Endoscopic Resection Treatment Decision

Introduction/Objective Accurately assessing submucosal invasion depth in pT1b esophageal squamous cell carcinoma (ESCC) is essential for determining additional treatment following endoscopic resection (ER). Disruption of the muscularis mucosae by cancer invasion leads to inconsistent evaluations of invasion depth. We evaluated interobserver agreement among gastrointestinal pathologists in measuring invasion depth and aimed to identify the most reliable method. Methods/Case Report Thirty-four pT1b ESCC specimens obtained by ER were retrospectively analyzed. Three pathologists independently measured submucosal invasion depth on Hematoxylin and Eosin (H&E)- and desmin-stained slides using three methods: 1, from an imaginary line representing original muscularis mucosae; 2, from a reconstructed trajectory based on disorganized muscularis mucosae; 3, from a line connecting the lowest visible ends of disrupted muscularis mucosae. Each method measured perpendicularly to the deepest point of invasion. Lesions were classified as pT1a-MM, pT1b-SM1 (≤200 μm), or pT1b-SM2 (>200 μm). Interobserver agreement was evaluated using Fleiss’ kappa (κ) and intraclass correlation coefficient (ICC). Results On H&E-stained slides, κ/ICC values were 0.607/0.611 (Method 1), 0.424/0.779 (Method 2), and 0.678/0.789 (Method 3). On desmin-stained slides, values were 0.496/0.623 (Method 1), 0.615/0.801 (Method 2), and 0.579/0.790 (Method 3). Conclusion Method 3 showed the highest agreement on H&E-stained slides, and Method 2 on desmin-stained slides demonstrated comparable reliability.