CEACAM5 and colorectal carcinoma: Tumor‐related serum markers, such as carcinoembryonic antigen (CEA) or carbohydrate antigen 19.9 (Ca19.9) are currently used in standard clinical practice, but their sensitivity ranges from 29 to 64%,15, 16 and their expression at baseline is widely heterogeneous, thus questioning their usefulness in follow up after CRC resection.