Molecular characterization of 54 cases of false-negative fine-needle aspiration among 1347 papillary thyroid carcinomas.

BACKGROUND: Fine-needle aspiration (FNA) has been widely accepted as the most crucial step in the preoperative assessment of thyroid nodules, but the false-negative rates are generally reported to be between 3.6% and 10.2%. To lower the overall incidence of this false-negative testing, new reporting systems encourage the molecular testing of thyroid nodules. However, to the authors' knowledge, the role of molecular testing in false-negative FNA has not yet been evaluated.

METHODS: In total, 1347 consecutive papillary thyroid carcinomas (PTCs) with both cytological and histological diagnoses were collected from the same center. A blinded revision of the false-negative cases was performed. An analysis of the BRAF and Ras genes in the false-negative cases was then performed.

RESULTS: The false-negative rate at the time of primary FNA diagnosis was 4.8% (65 of 1347 cases). False-negative cases were 15 follicular variant PTCs, 2 classical variant, and 1 solid variant that lacked peculiar PTC cytomorphological features. Adequate cellular material for molecular analysis was available only in 54 of the 65 false-negative cases. Mutations were found in 6 cases (11%), and Ras alterations were present in 16 cases (29.6%). The addition of molecular analysis decreased the false-negative rate to 0.4% (5 of 1347 cases).

CONCLUSIONS: The results of the current study confirm the feasibility of BRAF and Ras analysis in routine FNA. However, when the false-negative FNA rate is low, the cost-benefit analysis of the detection of BRAF and Ras mutations should be carefully evaluated. Consequently, the authors suggest that preoperative molecular assessment could be helpful for benign nodules, but only in the presence of clinical suspicion of malignancy.