The measurement of serum levels of the extracellular biomarker CEA is routinely carried out for the monitoring of adenocarcinoma growth as well as efficacy of its treatment.(12) Under physiologic conditions, CEA – the product of the CEACAM5 gene(13) – is mainly expressed on the apical surface of the gastrointestinal epithelium, and only low amounts of soluble CEA (approximately ≤5 ng/mL) can be detected in serum. This evidence concerns the gene CEACAM5 and adenocarcinoma.