Fine-needle aspiration of thyroid nodules: correlation between cytology and histology and evaluation of discrepant cases.

Abstract

The purpose of this study was to evaluate the results of thyroid fine-needle aspiration (FNA) and to determine the reasons for the discrepancies between the cytologic and histologic diagnoses. The authors evaluated the cytologic and histologic results of 133 FNAs obtained from 92 patients who underwent subsequent thyroidectomies. The initial cytologic results were indeterminate in 39 of 133 cases (29%) because a neoplasm could not be ruled out. These cases corresponded histologically to 9 adenomatoid nodules (ANs), 14 follicular adenomas (FAs), and 16 malignant thyroid neoplasms. The reported FNA diagnoses of the remaining 94 cases (71%) were 48 ANs, 19 follicular neoplasms (FNs), 21 papillary carcinomas (PCs), and 6 cases of Hashimoto's thyroiditis (HT). Correlation of cytology and histology showed that 69 of 94 FNA results (73%) correlated with the histologic diagnoses, whereas 25 (27%) were discrepant. The discrepancies resulted from cytodiagnostic errors in 13 cases (52%), suboptimal smears in 11 (44%), and an FNA sampling error in 1 (4%). The false-negative rate of FNA was 19% and the false-positive rate was 6%. Diagnostic pitfalls and indeterminate FNA diagnoses were predominantly due to overlapping cytologic criteria between ANs, FNs, and follicular variants of PCs. Rendering a definite diagnosis on suboptimal FNA samples is also a significant source of pitfalls.