Therefore, molecular screening with NGS is becoming a standard of care for BTC; (4) even if looking for IDH1 and/or FGFR fusion is more relevant in iCCA, NGS allows an identification of several potential actionable targets and it is interesting to be performed regardless of primary tumor localization (e.g., EGFR and HER2 in eCCA and GBC); (5) in addition to solid tissue biopsies, the place of ‘liquid biopsies’ (ctDNA), allowing repeated molecular profiling in a less invasive way, still needs to be validated in BTC. The gene discussed is IDH1; the disease is neoplasm.