Chapter 6d

Fine-needle aspiration (FNA) biopsy of the thyroid gland is an accurate diagnostic test used routinely in the initial evaluation of nodular thyroid disease (1-6). Epidemiologic studies suggest that nodular thyroid disease is a common clinical problem, with a prevalence of 4% to 7% in the adult population in North America and an annual incidence of 0.1%, which translates into approximately 300,000 new nodules in the United States (1). A survey of clinical members of the American Thyroid Association revealed that most endocrinologists (96%) perform FNA biopsy for diagnosis of thyroid nodules (7). In addition, FNA with ultrasonographic guidance (US-FNA) is used routinely in follow-up surveillance of patients with thyroid cancer. Therefore, we estimate that more than 300,000 thyroid FNA biopsies will be performed this year in the United States alone. Worldwide, the number of thyroid aspirations is most likely in the millions. Thus, the importance of FNA biopsy in thyroid practice cannot be overemphasized.