The high serum CEA detected through CRC screening programs should be considered a marker of malignancy, especially in patients with appropriate symptoms, which include diarrhoea or constipation, changes in stool consistency, narrow stools, rectal bleeding or blood in the stool, pain, cramps, or gas in the abdomen, pain during bowel movements, Irritable Bowel Syndrome (IBS), change in bowel habits, continual urges to defecate, weakness or fatigue, unexplained weight loss, shortness of breath, and iron deficiency anaemia. This evidence concerns the gene CEACAM5 and Iron deficiency anemia.