carcinoembryonic antigen (CEA) /kär′sənō·em′brē·on″ik/ [Gk, karkinos, crab, en, into, bryein, to grow, anti, against, genein, to produce] , an antigen present in very small quantities in adult tissue. Changes in CEA values are used to monitor tumor response to treatment. The reference range for serum CEA is 0-3 ng/mL in nonsmokers and 0-5 ng/mL in smokers.
