Increased Serum Carcinoembryonic Antigen Levels as An Early Sign of Medullary Thyroid Carcinoma

Abstract

To emphasize the potential association between increased levels of carcinoembryonic antigen (CEA) and the presence of medullary thyroid carcinoma (MTC). We present two case reports of this association, including long-term serial measurements of CEA in one patient. CEA is a tumor marker often associated with colon cancer. In recent years, increased CEA in plasma has been reported in patients with other cancers. Diagnoses of MTC in two patients were preceded by increased CEA levels (for 6 years in one patient). Because CEA levels returned to normal after thyroidectomy, MTC may have been the cause of the increases. In patients with increased plasma CEA levels, MTC should be considered in the differential diagnosis even if thyroid palpation is nonrevealing and thyroid function is normal.