From the comparison of CEA and Septin 9 in the same patients, the specificity of the CEA assay was 85.2% (23/27), higher than the Septin 9 specificity (70.4%; 19/27); however Septin 9 was much more sensitive (100%; 27/27) in cancer samples than CEA (51.8%; 14/27). This evidence concerns the gene CEACAM5 and cancer.