Diagnostic pitfalls in thyroid fine‐needle aspiration: A review of 394 cases

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Abstract
To determine the diagnostic pitfalls of thyroid fine‐needle aspiration (FNA), we reviewed 394 thyroid aspirates obtained between January 1986 and December 1990. Surgical follow‐up was available for 150 aspirations. The cytologic diagnoses were categorized into four groups: benign, 57; indeterminate, 51; malignant, 33; and nondiagnostic specimen, nine. There were three false negative diagnoses (3%), which upon review were judged to be inadequate specimens. Three false positive diagnoses (7%) were identified: in the first two cases, follicular adenomas were mistaken for papillary carcinoma: in the third case, atypical Hürthle cells were mistaken for a Hurthle cell carcinoma. Our results showed a sensitivity of 93% and a specificity of 91% for the detection of malignancy. If indeterminate cases were considered positive, the specificity decreased to 50%, while the sensitivity increased to 97%. We conclude that: 1 certain follicular adenomas may display cytologic features mimicking papillary carcinoma; 2 as in follicular neoplasms, aspirates of Hürthle cell adenomas cannot be differentiated from Hurthle cell carcinomas; 3 with adequate sampling, false negative results can be markedly reduced.