Evolving techniques to optimize ERCP-based sampling and evaluation of malignant biliary strictures

Endoscopic retrograde cholangiopancreatography (ERCP)-based tissue acquisition is the cornerstone for assessment of suspected malignant biliary strictures. Conventional techniques, including biliary brush cytology and transpapillary forceps biopsy, are highly specific but are limited by modest sensitivity for detection of malignancy, often leaving a substantial proportion of individuals without a definitive diagnosis. To improve diagnostic sensitivity for cancer, several adjunctive approaches have been integrated into ERCP-based sampling. Peroral cholangioscopy (POC)-guided biopsies have become a reliable ERCP-based adjunctive modality, allowing direct visualization and targeted sampling, particularly in individuals with prior nondiagnostic procedures. Fluorescence in situ hybridization (FISH) is a technique used to improve diagnostic yield with biliary brushings by detecting chromosomal abnormalities, but is limited to specialized centers due to the need for specialized processing and training. Next-generation sequencing provides high sensitivity and can enable identification of actionable genomic alterations, while methylated DNA markers represent a promising, scalable molecular approach with strong diagnostic performance. Additional techniques include artificial intelligence-augmented direct visualization by POC and bile-based liquid biopsy. Current guidelines recommend multimodal ERCP-based sampling, combining at least two modalities where feasible, to optimize diagnostic accuracy. This review highlights the clinical performance, strengths, and limitations of established and emerging ERCP-guided techniques, emphasizing their evolving role in improving the diagnosis and management of malignant biliary strictures.