There are many novel diagnostic biomarkers for CCA, such as carbohydrate antigen 19-9 (CA19-9), carcinoembryonic antigen (CEA), and imaging features, whereas the diagnosis efficiency of those approaches is still unsatisfactory (Sinakos et al., 2011; Liang et al., 2015; Chen et al., 2018; Silsirivanit et al., 2020). Here, CEACAM5 is linked to cholangiocarcinoma.