CARCINOEMBRYONIC ANTIGEN - NO HELP WITH THE DIFFERENTIAL-DIAGNOSIS

Two patients who were referred because of an increase in serum carcino -embryonic antigen (CEA) were diagnosed after a number of years as hav ing a medullary thyroid carcinoma. The relationship between CEA and me dullary thyroid carcinoma is discussed. The serum level of CEA is neit her sensitive nor specific enough to serve as a diagnostic tool. Its d etermination, however, is useful in the follow-up of patients with car cinoma of the breast, cole-rectal carcinoma and medullary thyroid carc inoma.