To date, several serum markers, including the clinically available iCA19–9 and CEA, and potential markers such as CA242, mucin glycoproteins, and several cytokines have been reported to be adequate diagnostic and prognostic markers for CCA.58 Yet, the diagnostic accuracy of such markers is not sufficient for a timely and reliable diagnosis of CCA. Here, CEACAM5 is linked to cholangiocarcinoma.