CEACAM5 and rectal cancer: CA199 is a high-molecular-weight low glycolipid that is present in the form of sialomucin in the serum and is widely distributed on the cytomembrane and currently is used for the diagnosis of rectal cancer [13] However, the poor sensitivity and specificity of CEA and CA199 limit the use of only these biomarkers in the diagnosis of rectal cancer [14].