CEACAM5 and colorectal carcinoma: Multiple serum markers including carcinoembryonic antigen (CEA), carbohydrate antigen 19-9 (CA19-9), carbohydrate antigen 242 (CA242) [6], and alpha-fetoprotein (AFP) [7] have been well recognized as tumor markers for CRC, as well as neuron specific enolase (NSE) [8], cytokeratin 19 (CK19) [9], squamous cell carcinoma antigen (SCC) [10], complexed prostate-specific antigen (c-PSA) [11], carbohydrate antigen 125 (CA125) [12], and carbohydrate antigen 72-4 (CA72-4) [13].