CEACAM5 and neoplasm: It is well known that carcinoembryonic antigen (CEA) and carbohydrate antigen 199 (CA199) are popular tumor biomarkers for the CRC, however, studies shown that both serum CEA and CA199 have been showed unsatisfactory performance in CRC screening 5, 6, both of them are recommended as circulating tumor markers in CRC for tumor detecting and monitoring responses to therapy according to the European Society for Medical Oncology (ESMO) and Chinese Society of Clinical Oncology (CSCO) clinical practice guidelines for CRC diagnosis 7, 8.