The carcinoembryonic antigen (CEA) is normally presented at very low levels in the blood but it may be elevated with certain types of cancer. Its normal range is below 5 ng/mL for healthy non‐smokers and below 10 ng/mL for smokers; however, in cancerous patients, its value in the blood usually exceeds the threshold value so it has been considered as a cancer biomarker.4, 5. This evidence concerns the gene CEACAM5 and cancer.