What is the role of lab testing in the workup of follicular thyroid carcinoma (FTC)?

Updated: Jun 18, 2020
  • Author: Luigi Santacroce, MD; Chief Editor: Neetu Radhakrishnan, MD  more...
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Current guidelines from the National Comprehensive Cancer Network recommend that patients with thyroid nodules undergo measurement of thyroid-stimulating hormone (TSH) and ultrasound of the thyroid and central neck; ultrasound of the lateral neck may be considered. Patients with thyroid nodules and a low TSH level should have radioiodine imaging: if this study reveals an autonomously functioning (“hot”) nodule, the patient should be evaluated for thyrotoxicosis. [1]

Patients with hypofunctional nodules, and those with a normal or elevated TSH level, should be considered for fine-needle aspiration biopsy (FNAB), based on clinical and sonographic features. A cytologist could experience difficulty in distinguishing some benign cellular adenomas from their malignant counterparts (ie, follicular and Hürthle cell adenomas from carcinomas). On final pathologic assessment, approximately 15-40% of FNAB samples with a cytologic diagnosis of “suspicious for follicular neoplasm” prove to be malignant. [1]

A prognostic indicator of significant value may be RAS genotyping by polymerase chain reaction (PCR), which may help in the clinical and histologic reassessment of these tumors. In thyroid nodules with otherwise indeterminate cytology, the presence of RAS mutation may potentially alters initial surgical management, as it indicates a markedly elevated increased risk for cancer (∼85%). [18]

Determining the serum level of carcinoembryonic antigen (CEA) may be helpful; the reference value is less than 3 ng/dL. However, the implications of CEA elevation are not specific because CEA levels are elevated in several cancers, and many healthy people may have small amounts of CEA, especially pregnant women and heavy smokers.

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