CEACAM5 and colorectal carcinoma: There have been many studies on the clinical use of protein tumor markers such as serum carcinoembryonic antigen (CEA), carbohydrate antigen 19-9 (CA 19-9), carbohydrate antigen 125 (CA 125), carbohydrate antigen 242 (CA 242), carbohydrate antigen 153 (CA 153), carbohydrate antigen 72-4 (CA 72-4), squamous cell carcinoma (SCC), and cytokeratin-19-fragment (CYFRA 21-1) in the diagnosis of CRC, but the role of these markers in the screening of precancerous lesions and early CRC was rarely investigated [8,9,10,11].