Accuracy of Fine-Needle Aspiration of Thyroid

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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.