CEACAM5 and colorectal cancer: CA19-9 has several limitations, such as poor specificity, a lack of expression in the Lewis-negative phenotype, and a higher false-positive rate in the presence of obstructive jaundice.[40] Both CEA and CA-50 have a low sensitivity and specificity, and CEA is the standard tumor marker for screening and predicting the prognosis of colorectal cancer.[41]