Practical guidelines for molecular testing of cholangiocarcinoma in clinical practice: Italian experts' position paper.

Biliary tract cancers (BTCs) represent a spectrum of malignancies associated with a dismal prognosis. Recent genomic profiling studies have provided a deeper understanding of the complex and heterogenous molecular landscape of BTCs, identifying several actionable genetic alterations, and expanding treatment options. Due to the high number and complexity of genetic alterations which require testing, next-generation sequencing (NGS) is currently the preferred approach over conventional methods (i.e., immunohistochemistry, fluorescence in-situ hybridization and PCR) for molecular profiling of BTCs and should be performed upfront in all BTC patients. However, BTC sampling often yields low tumor cellularity tissue, hampering NGS analysis. Future perspectives to overcome this obstacle include liquid biopsy and optimization of biopsy protocols. In this position paper, the authors discuss the current histopathologic, molecular, and therapeutic landscape of BTCs, provide a critical overview of the available testing methods for molecular diagnostics, and propose a practical diagnostic algorithm for molecular testing of BTC samples.