Intrahepatic Cholangiocarcinoma Staging and Classification Systems: An Updated Narrative Review

Background Intrahepatic cholangiocarcinoma (ICC) is an aggressive primary liver malignancy characterized by increasing incdence, late diagnosis, and marked biological heterogeneity. This review summarizes ICC staging and classification systems, highlighting their clinical applications, strengths, limitations, and future development. Methods Anatomical, histopathological, imaging-based, and molecular classifications were examined, with particular attention to prognostic discrimination, surgical planning, and treatment selection. Results The AJCC eighth-edition TNM system remains the international standard and improves prognostic stratification through assessment of tumor size and number, vascular invasion, peritoneal perforation, extrahepatic extension, nodal involvement, and distant metastases. However, TNM staging does not fully capture biological heterogeneity. Macroscopic growth patterns and the World Health Organization distinction between large duct-type and small duct-type ICC provide complementary prognostic and surgical information. Institutional and morphology-based systems may refine postoperative risk assessment but have limited generalizability. Molecular profiling identifies clinically relevant subgroups characterized by FGFR2 fusions, IDH1/2 mutations, BAP1 and ARID1A alterations, or KRAS and TP53 mutations, with therapeutic implications. Conclusion Contemporary ICC assessment should combine TNM stage with morphological, pathological, and molecular features. Future multidimensional frameworks incorporating tumor biology, treatment response, and circulating biomarkers may improve prognostication and personalized management, provided that international validation, accessibility, and clinical usability are maintained.