That is why, in certain situations, there is the possibility to assess the concentration of tumor-associated proteins in medical laboratories, such as carcinoembryonic antigen (CEA) and, in some cases, carbohydrate antigen 19-9 (CA 19-9), which are also used in cases of patients with CRC, although their diagnostic sensitivity and specificity are considered poor [37]. Here, CEACAM5 is linked to colorectal carcinoma.