CEACAM5 and neoplasm: underscored mSEPT9's superiority over CEA in three key aspects of evaluating surgical outcomes: a higher proportion of patients could be assessed using mSEPT9, reflecting its higher preoperative detection sensitivity; postoperative mSEPT9 levels showed a more significant decrease than CEA, aiding in clearer differentiation of treatment effects; and a positive correlation was observed between tumor size and mSEPT9 levels, suggesting its utility as a quantitative marker for monitoring tumor progression or regression, a correlation not seen with CEA.