CEACAM5 and signet ring cell carcinoma: In recent decades, more pathological factors, for example, venous or lymphatic invasion and perineural invasion; cellular factors, for example, poor differentiation, mucinous adenocarcinoma or signet-ring cell carcinoma, and high CEA level; and molecular factors, for example, ras gene mutation, B-raf gene mutation, microsatellite instability, and CpG island methylator phenotype, have been confirmed to be associated with the prognosis of colorectal cancer.19,20 However, the existing TNM staging system does not take the above factors into consideration.