Accuracy of Fine-Needle Aspiration of Thyroid

Abstract

CONTEXT: Fine-needle aspiration has become an accepted and cost-effective procedure for rapid diagnosis of thyroid lesions. The routine use of fine-needle aspiration has reduced the rate of unnecessary surgery for thyroid nodules. OBJECTIVES: To determine the accuracy of fine-needle aspiration biopsy diagnosis and to discuss the possible pitfalls. Design, Setting, and Participants.-Reports of 6226 fine-needle aspiration biopsies of the thyroid performed during a period of 16 years (1982-1998) were reviewed. Computerized reports of the fine-needle aspiration biopsies were sent to the physicians who performed the procedures, and clinical follow-up information regarding the patients was requested. Twenty-four clinicians participated in the study. Histologic diagnoses were available for 354 cases. The cytopathologic diagnoses were correlated with the histologic findings or clinical outcomes. RESULTS: The cytologic diagnoses were as follows: 210 (3.4%) malignant, 450 (7.2%) suspicious, 3731 (60%) benign, and 1845 (29.5%) unsatisfactory. Most of the cases with negative or unsatisfactory aspirates were followed clinically or by repeat fine-needle aspiration. We identified 11 false-negative and 7 false-positive diagnoses. For aspirates considered sufficient for diagnosis, the sensitivity and specificity levels were 93% and 96%, respectively. CONCLUSIONS: Fine-needle aspiration of the thyroid gland is highly accurate and has a low rate of false-negative and false-positive diagnoses. The major diagnostic problems are caused by diagnosis using a marginally adequate specimen, diagnosis of malignancy based on just 1 or 2 atypical cytologic features, or overlapping cytologic features of follicular neoplasm with those of follicular variant of papillary carcinoma.