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Aim: Investigate the role of BRAF V600 mutation testing in identifying thyroid carcinoma from FNA samples.Methods: Over an 8 month period thyroid fine needle aspirates (FNA's) reported as Thy 3F (neoplasm possible/suggestive of follicular neoplasm equivalent Bethesda Class IV), Thy4 (suspicious of malignancy equivalent Bethesda Class V) & Thy 5 malignant (equivalent Bethesda Class VI) were tested for BRAF V600 mutation & managed as malignant if mutations were present. Results: Of 207 FNA's, 5 were Thy 5, 19 Thy 4, 36 Thy 3f, 13 Thy 3a, 84 Thy 2 & 50 Thy 1. 29 Thy 3f, Thy 4, or Thy 5 FNA's were tested for BRAF V600 mutation and 7 of 29 (24 %) showed evidence of mutation. Four patients with BRAF V600 mutation underwent surgery to remove all thyroid tissue, one patient received a right lobectomy for technical reasons and two patients are awaiting total thyroidectomy. All patients with BRAF V600 mutation were found to have malignancy on final histology, with a diagnostic sensitivity for malignancy excluding co-incidental microcarcinoma of 100% and specificity of 42%. BRAF V600 mutation is 100% specific for thyroid carcinoma, if a lesion is a primary thyroid tumour. Conclusion: BRAF V600 mutational analysis enables single stage total thyroidectomy for carcinoma if gene mutation is present in pre-operative FNA. BRAF V600 testing potentially reduces the need for completion thyroidectomy with significant cost savings and lowers patient morbidity associated with completion thyroidectomy in cases where the cytology does not show definite features of malignancy but where BRAF V600 mutation is identified in pre-operative thyroid FNA. [ABSTRACT FROM AUTHOR]