Widely used tumour serum markers, such as CA19-9 or CEA, lack sensitivity and specificity since their levels are often normal in PDAC early stages or are falsely high in individuals with other pathological conditions (due to concomitant obstruction of the intrahepatic bile ducts caused by tumours located in the pancreatic head, usually associated with jaundice and high bilirubin levels) [16]. Here, CEACAM5 is linked to neoplasm.