Updated protocols for biliary brush cytology significantly improve sensitivity in diagnosing perihilar and intrahepatic cholangiocarcinoma.

• Sensitivity jumped from 50.5% to 88.3% after protocol changes, with first sample sensitivity reaching 78%.
• Specificity remained high at 100% across both prospective and historical cohorts.

These results suggest that adopting optimized protocols can enhance diagnostic accuracy, potentially improving patient selection for surgery.

• Next-generation sequencing and additional samples further boosted sensitivity to 83% and 85%, respectively.