The Clinicopathological Characteristics and Prognosis of Cholangiolocarcinoma: A Multicenter Study With a Central Pathology Review

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BACKGROUND: Cholangiolocarcinoma (CLC) is a rare liver cancer with ≥ 80% ductular configuration (DC). Given its rarity, its clinicopathological characteristics remain poorly understood, and its status as a distinct disease entity remains controversial. We conducted a nationwide multicenter study with centralized pathological review to investigate the features of CLC. METHODS: We included patients with a postoperative diagnosis of CLC at 49 participating institutions (2005-2018). All cases were re-evaluated by centralized pathology according to the WHO classification. RESULTS: Among 196 re-evaluated patients, 56 tumors were classified as CLC, 69 as intrahepatic cholangiocarcinoma (iCCA) with < 80% DC, 53 as small-duct type iCCA with DC, and 16 as mixed small- and large-duct type (SD/LD-iCCA with DC). CLC showed a low prevalence of viral hepatitis (23.2%), frequent arterial enhancement (83.9%), and characteristic apical EMA positivity. The median overall survival (OS) was 10.8 years, with 5- and 10-year OS rates of 85.0% and 73.7%, respectively, which were significantly better than those of SD/LD-iCCA with DC. Recurrence occurred in 38.2% of CLC cases with favorable outcomes following surgical resection. CONCLUSIONS: CLC exhibits distinct pathological and prognostic features, including favorable long-term survival, supporting CLC as a distinct clinicopathological entity. Further molecular research is needed to refine the classification. TRIAL REGISTRATION: This study was registered with the UMIN Clinical Trials Registry (UMIN000057919).