When breast cancer patients are routinely reviewed for carcinoembryonic antigen after surgery, some values may be higher than others, but this does not necessarily mean that breast cancer is recurrent. This is because the postoperative carcinoembryonic antigen of breast cancer patients is determined by the immune status of the body or the specific condition. Some carcinoembryonic antigen, even if it is high, does not necessarily mean that it is a recurrence, while some carcinoembryonic antigen with normal value may have distant metastases, even including recurrence. In order to diagnose whether breast cancer is recurrent or not, in addition to monitoring the carcinoembryonic antigen, CT or ultrasound scans should be performed on the local excised area of the breast, and nuclear scans should be performed on the distant organs, including lung, liver, bone, brain and bone tissue of the whole body to determine whether there is recurrence or metastasis.