Mutational analysis of BRAF in fine needle aspiration biopsies of the thyroid: a potential application for the preoperative assessment of thyroid nodules.
BACKGROUND
Fine needle aspiration (FNA) is routinely used in the preoperative evaluation of thyroid nodules, but subsequent patient management is often complicated by the inability to decisively recognize malignancy on cytologic grounds alone. Activating mutations of the BRAF oncogene commonly occur in papillary thyroid carcinomas (PTCs) but not in other types of benign and malignant thyroid lesions. Mutational analysis of FNAs could enhance selection of thyroid nodules for surgical removal.


METHODS
Ninety-five excised PTCs along with 49 corresponding FNAs were evaluated for BRAF mutations by a newly developed assay that uses a novel primer extension method (MutectorR assay) and by direct sequencing. An additional 42 FNAs from thyroid nodules that were excised based on a suspicion of malignancy were also evaluated.


RESULTS
BRAF mutations were identified in 36 of the 95 (38%) excised PTCs. By histological subtype, BRAF mutations were more common in conventional PTCs than in the follicular variant (67% versus 12%; P < 0.0001; chi(2)). Analysis of the preoperative FNAs accurately reflected BRAF status of the resected PTC in 46 of the 49 paired samples (94% concordance). In FNA samples grouped according to the preoperative cytologic findings (malignant, n = 25; benign, n = 11; and indeterminate, n = 55), a BRAF mutation confirmed the diagnosis of PTC in 72% of carcinomas within the malignant group, and it established the diagnosis of PTC in 16% of carcinomas within the indeterminate group. BRAF mutations were not detected in FNAs from 32 benign thyroid lesions. Direct sequencing and the MutectorR assay yielded completely concordant results.


CONCLUSIONS
BRAF mutations are common in conventional PTCs, and they are specific for PTC. A BRAF mutation can be reliably detected in cells aspirated from a thyroid nodule suggesting a role for this marker in the preoperative evaluation of thyroid nodules.
Cohen
Yoram
Y
Department of Otolaryngology, and Head and Neck Surgery, Division of Head and Neck Cancer Research, The Johns Hopkins Medical Institutions, Baltimore, Maryland, USA.
Rosenbaum
Eli
E
Clark
Douglas P
DP
Zeiger
Martha A
MA
Umbricht
Christopher B
CB
Tufano
Ralph P
RP
Sidransky
David
D
Westra
William H
WH
D044963:Biopsy, Fine-Needle; D018265:Carcinoma, Papillary, Follicular / Q000235:genetics*; D004247:DNA / Q000378:metabolism; D004252:DNA Mutational Analysis; D006801:Humans; D009154:Mutation; D016133:Polymerase Chain Reaction; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics*; D017422:Sequence Analysis, DNA; D013961:Thyroid Gland / Q000473:pathology; D013964:Thyroid Neoplasms / Q000175:diagnosis* / Q000235:genetics* / Q000473:pathology
D004247:DNA; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf