Small but significant: Prognostic value of the small duct type in intrahepatic cholangiocarcinoma

Abstract

This study aimed to evaluate the clinicopathological features, prognostic relevance, and classification accuracy of histological subtypes—the small duct type and the large duct type—in intrahepatic cholangiocarcinoma (iCCA) based on the WHO 5th edition criteria. A retrospective analysis was conducted on iCCA cases classified into the small duct type and the large duct type. Key pathological variables were identified using logistic regression and used to develop a random forest classification model. Survival outcomes were analyzed using Kaplan-Meier and Cox regression analyses. The random forest model, using nine significant pathological features, achieved an overall classification accuracy of 83 %. Mucin production, tumor grade, and intraepithelial lesion were among the most influential predictors. The small duct type was associated with significantly better overall survival (5-year rate: 57.6 %) and recurrence-free survival (46.6 %) compared to the large duct type (24.9 % and 20.6 %, respectively). Multivariable analysis confirmed the large duct type as an independent predictor of worse prognosis. Histological subtyping of iCCA holds important prognostic value. The small duct type is associated with a more favorable clinical course, supporting the integration of subtype-aware assessments into diagnostic and prognostic frameworks. These findings may inform future developments in computational pathology and personalized treatment strategies.