Sonographically guided fine needle aspiration of thyroid nodule: Discrepancies between cytologic and histopathologic findings

Purpose. To analyze the discrepancies between the cytologic results of sonographically (US)-guided fine needle aspiration (FNA) of thyroid nodules and final histopathologic results and to discuss the limitations of US-guided FNA. Materials and Methods. The results of US-guided FNAs performed by a single experienced radiologist in 315 thyroid nodules in 292 patients (246 women, 46 men aged 12-79 years) were retrospectively correlated with their surgical pathologic results. The FNA results were classified as nondiagnostic, indeterminate, negative, or positive, whereas final pathologic diagnoses were classified as malignant or benign. Results. The FNA results were nondiagnostic in 31 cases (9.8%), indeterminate in 97 cases (30.8%), and determinate in 187 cases (59.4%). Of the 187 conclusive cases, 169 (90.4%) were concordant with the final pathologic results, whereas 18 (9.6%) were discordant with 14 false-positive and 4 false-negative results. These discrepancies were caused by atypical nuclear features. Among the 97 indeterminate and 31 non-diagnostic cases, a malignancy was found in 14 (14.4%) and 8 (25.8%) cases, respectively. In addition, 10 papillary carcinomas, which were not visualized on sonograms, were detected incidentally in thyroidectomy specimens. Conclusion. The diagnostic accuracy of US-guided FNA of thyroid nodule has limitations that should be minimized by careful interpretation of the cytologic findings and accurate sampling.