Detection of BRAF^V600E mutation on fine needle aspiration specimens of thyroid nodule refines cyto‐pathology diagnosis, especially in BRAF^V600E mutation‐prevalent area

Abstract

BACKGROUND: Between 10 and 30% of the fine needle aspiration biopsies (FNABs) of thyroid nodules are diagnosed as 'indeterminate'. A molecular diagnostic method is needed to reduce unnecessary surgery in this group. In Korea, most thyroid cancer is the classic papillary type and the BRAF(V600E) mutation is highly prevalent. AIM: To evaluate the role of pre-operative detection of BRAF(V600E) mutation in the FNAB specimens of thyroid nodules in a BRAF(V600E) mutation-prevalent geographical area. PATIENTS AND METHODS: In 137 specimens of FNAB (107 papillary thyroid carcinomas (PTC); 3 follicular thyroid carcinomas (FTC); 2 undifferentiated thyroid carcinomas; 25 benign lesions), both direct DNA sequencing and PCR-RFLP were used for detecting the BRAF(V600E) mutation. The sensitivity and specificity were calculated. We analysed the association between BRAF(V600E) mutation and the clinico-pathological parameters. RESULTS: The BRAF(V600E) mutation was present in 93 (83%) of 112 thyroid cancers. Direct DNA sequencing showed a sensitivity of 83.0% and a specificity of 96.0%. The sensitivity and specificity of PCR-RFLP were 78.6% and 80.0%, respectively. Among 25 cases with indeterminate FNAB cytology, 8 patients had malignant lesions (5 PTC and 3 FTC). Three (60%) of 5 PTCs and 1 out of 17 benign lesions had BRAF(V600E) mutation (only one false positive case and the definitive pathology showed atypical nodular hyperplasia that could be a premalignant lesion). The diagnostic accuracy of this molecular method in only the 25 indeterminate nodules was 76% (19/25). No mutation was found in 3 FTCs. Among 107 PTCs, there was no significant association of the BRAF(V600E) mutation with the known risk factors. CONCLUSION: Detection of the BRAF(V600E) mutation in FNAB specimens refines the FNAB-cytology diagnosis, especially in a BRAF(V600E) mutation-prevalent area. Direct DNA sequencing was a more reliable method than PCR-RFLP for detecting the BRAF(V600E) mutation with a high sensitivity and specificity.