However, positron emission tomography (PET) revealed no abnormal uptake, and the levels of tumor markers were within normal limits (CEA, 1.3 ng/mL; CA19-9, 20.3 U/mL) (Fig. 2b); hence, the possibility of metastasis was considered to be low, and the patient was placed under observation. Here, CEACAM5 is linked to neoplasm.