Cholangiocarcinoma: The era of liquid biopsy

Table 1 Tissue biopsy remains the gold standard technique for diagnosis at present

Liquid biopsy	Tissue biopsy
Advantages
Minimally invasive-easy sampling	Histological evaluation
Serial analysis-tumour evolution monitoring	Clinically validated and standardised
Ability to assess drug response-drug resistance	Available in most hospitals
Ability to use for postoperative follow-up/surveillance	Provides a direct sample of tumour tissue, ensuring accurate pathological analysis
Fast	Facilitates detailed genetic and molecular profiling of the sampled tissue
Comprehensive tumour profiling
Applicable to inaccessible tumours
Reveals tumour heterogeneity
Lower cost of sample isolations
Disadvantages
Not clinically validated	Invasive procedure
No histological evaluation	Not applicable in inaccessible tumours
Low availability	Localised tissue sampling
Low sensitivity (may miss low-abundance mutations or those not shed into the bloodstream	No capacity for tumour evolution monitoring, drug response-drug resistance monitoring, tumour heterogeneity assessment
Technology-dependent	Time intensive procedure
High costs (in case of NGS and WGS)	Higher cost of sample isolations

NGS: Next generation sequencing; WGS: Whole genome sequencing.