We examined CEA expression in tumor tissues (t-CEA) by immunohistochemical staining instead of preoperative CEA in serum (s-CEA), for the following two reasons: (a) for most patients in our study preoperative s-CEA was not detected; and (b) the prognosis value of t-CEA may be stronger than that of s-CEA in CRC due to the fact that level of s-CEA is affected by many factors, such as liver diseases, bowel obstruction and smoking, which could influence CEA production, release and metabolism [64]. This evidence concerns the gene CEACAM5 and liver disorder.