Role of serum carcinoembryonic antigen in preoperative diagnosis of cancer in patients with thyroid nodules.

Serum carcinoembryonic antigen (CEA) was measured by double antibody radioimmunoassay technique in 95 normal subjects and in 258 patients with thyroid nodules. All the normal subjects and the patients with benign nodules had normal CEA values. Increased serum CEA levels (above 50 ng/ml) were found in all medullary and undifferentiated (giant cell) carcinomas. After surgery, the CEA fell within the normal range in the patients with medullary carcinoma. High levels of CEA were also present in 26% of differentiated carcinomas. A relationship between high CEA values and the presence of metastatic disease was not found. Measurement of serum carciniembryonic antigen may be useful in the preoperative diagnosis of cancer in patients with thyroid nodules.