False-negative errors in fine-needle aspiration biopsy of dominant thyroid nodules: a prospective follow-up study.

Reluctance to adopt fine-needle aspiration (F-NA) of dominant thyroid nodules stems largely from fear of overlooking a malignancy in a nodule diagnosed as benign on FNA (false-negative error). Published error rates have been derived from surgical series without regard to the outcome of those who were followed without operation. In order to ascertain the overall false-negative error rate, we conducted a prospective study in 600 patients who underwent FNA. Among the 482 study patients who had a benign FNA diagnosis or inadequate specimens, 117 underwent surgery because of the concurrent large-needle biopsy result or a clinical suspicion of malignancy. Eight false-negative errors were identified in this group, 5 of which were detected by large-needle biopsy. Among the remaining 365 patients who were followed for an average of 2 1/2 years, 2 patients were found to have well-differentiated carcinomas in recurrent cysts. The overall false-negative error rate of FNA alone in all 482 patients was 2.1%. This was reduced to 1.0% by the use of concurrent large-needle biopsy. Properly applied, FNA can reduce unnecessary surgery among patients with clinically benign nodules without incurring an unacceptably high false-negative error rate. Furthermore, this error rate may be reduced substantially by combining large-needle biopsy with FNA and by close follow-up with surgery performed later in patients who manifest clinical features suggestive of malignancy.