The Cytomorphologic and Molecular Assessment of Bile Duct Brushing Specimens.

Biliary duct brushing cytology is the standard of care for the assessment of bile duct strictures but suffers from low sensitivity for the detection of a high-risk stricture. Pathologic diagnosis of strictures is optimized by integration of cytomorphology and molecular analysis with fluorescence in situ hybridization or next-generation sequencing. Bile duct cancers are genetically heterogeneous, requiring analysis of multiple gene panels to increase sensitivity. Using molecular analysis as an ancillary test for bile duct brushing samples aids in the identification of mutations that support the diagnosis of a high-risk stricture as well as the identification of actionable mutations for targeted therapies currently in clinical trials for the treatment of patients with bile duct cancer.