Thyroid fine-needle aspiration: the relevance of BRAF mutation testing

Comparison of diagnostic methods for the detection of a BRAF mutation in papillary thyroid cancer

The most common genetic alteration identified in papillary thyroid cancer (PTC) encodes a valine to glutamic acid change at position 600 (V600E) in the BRAF proto-oncoprotein. The most accurate and reliable method for detecting this BRAF mutation has not yet been determined. In the present study, the sensitivity, specificity and feasibility of diagnostic methods for BRAF mutations were assessed. BRAF mutational analysis was performed by Sanger DNA sequencing, using the Cobas^® 4800 BRAF V600 test and by immunohistochemistry (IHC). A total of 185 tumor tissues samples were analyzed using the three assays. BRAF mutations were identified in 76.2% of samples by Sanger sequencing, 78.9% of samples by Cobas 4800 BRAF V600 test and 76.8% of samples by IHC. Complete concordance for the three methods was observed in 92.4% of samples. Sensitivity and specificity of Sanger sequencing were 97.2 and 95.2%. Sensitivity and specificity of the Cobas 4800 BRAF V600 test were 99.3 and 90.5%. Sensitivity and specificity of IHC were 98.6 and 97.6%. Furthermore, the presence of a BRAF mutation was significantly associated with extrathyroid extension and multifocality (P<0.05), but not associated with age, sex, lymph node metastasis, central node metastasis, lateral node metastasis, Tumor-Node-Metastasis stage or tumor size in patients with PTC. These results suggest that a combination of IHC and the Cobas 4800 BRAF V600 Test kit for V600E mutation analysis is the most efficient and reliable method in routine practice. Accurate screening for BRAF mutation may contribute to improving the risk stratification of PTC.

Utility of including BRAF mutation analysis with ultrasonographic and cytological diagnoses in ultrasonography-guided fine-needle aspiration of thyroid nodules

This study investigated the role of BRAF mutation analysis in thyroid fine-needle aspiration (FNA) samples compared to ultrasonographic and cytological diagnoses. A total 316 patients underwent ultrasonography (US)-guided FNA with BRAFV600E mutation analysis to diagnose thyroid nodules. One hundred sixteen patients with insufficient US images (n = 6), follow-up loss (n = 43), or unknown final diagnosis (n = 67) were excluded from the study. Comparisons between US diagnoses, cytological diagnoses, and BRAF mutation analysis were performed. Of 200 thyroid nodules, there was US diagnosis with 1 false negative and 11 false positive cases, cytological diagnosis with 10 false negative and 2 false positive cases, and BRAFV600E mutation analysis with 19 false negative and 2 false positive cases. The sensitivity, specificity, positive and negative predictive values, and accuracy of BRAFV600E mutation analysis were 83.2%, 98.1%, 97.5%, 86.6%, and 91%, respectively. Of the 18 nodules with Bethesda category III, 9 were true positive, 6 were true negative, 3 was a false negative, and none were false positive on BRAF mutation analysis. In conclusion, we recommend that BRAFV600E mutation analysis only be performed for evaluating thyroid nodules with Bethesda category III, regardless of US diagnosis.

A combination of immunohistochemistry and molecular approaches improves highly sensitive detection of BRAF mutations in papillary thyroid cancer

The optimal method for BRAF mutation detection remains to be determined despite advances in molecular detection techniques. The aim of this study was to compare, against classical Sanger sequencing, the diagnostic performance of two of the most recently developed, highly sensitive methods: BRAF V600E immunohistochemistry (IHC) and peptide nucleic-acid (PNA)-clamp qPCR. BRAF exon 15 mutations were searched in formalin-fixed paraffin-embedded tissues from 86 papillary thyroid carcinoma using the three methods. The limits of detection of Sanger sequencing in borderline or discordant cases were quantified by next generation sequencing. BRAF mutations were found in 74.4 % of cases by PNA, in 71 % of cases by IHC, and in 64 % of cases by Sanger sequencing. Complete concordance for the three methods was observed in 80 % of samples. Better concordance was observed with the combination of two methods, particularly PNA and IHC (59/64) (92 %), while the combination of PNA and Sanger was concordant in 55 cases (86 %). Sensitivity of the three methods was 99 % for PNA, 94.2 % for IHC, and 89.5 % for Sanger. Our data show that IHC could be used as a cost-effective, first-line method for BRAF V600E detection in daily practice, followed by PNA analysis in negative or uninterpretable cases, as the most efficient method. PNA-clamp quantitative PCR is highly sensitive and complementary to IHC as it also recognizes other mutations besides V600E and it is suitable for diagnostic purposes.

Correlation between polymorphisms of BRAF gene and papillary thyroid carcinoma

BACKGROUND

Papillary thyroid carcinoma (PTC), which accounts for 80% of all thyroid cancers, has an increasing incidence over these years. Single nucleotide polymorphisms (SNPs) of BRAF were considered to be one of well-established risk factors leading to development of PTC. The aim of this study was to investigate whether the common mutations of BRAF could elevate significantly the risk of PTC in a Chinese population.

METHODS

Four SNPs (rs11762469, rs17623204, rs1267636 and rs3748093) of BRAF were selected through our filter by Haploview 4.2 software with HapMap databases. We used the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) to genotype the four SNPs in blood samples of 618 subjects (206 patients with PTC and 412 healthy controls). The correlation between BRAF polymorphisms and PTC risk was assessed using student t-test and chi-square test.

RESULTS

The results showed that mutation in rs3748093 was significantly associated with an increased risk of PTC in allele model (A allele vs. T allele, OR = 1·68, 95% CI = 1·16-2·43, P = 0·006), dominant model (TA + AA vs TT, OR = 1·64, 95% CI = 1·08-2·48, P = 0·019) and homozygote model (AA vs. TT, OR = 2·94, 95% CI = 1·00-8·61, P = 0·040). However, the other three SNPs (rs11762469, rs17623204 and rs1267636) were shown to have no association with the risk of PTC.

CONCLUSIONS

Our results indicated that polymorphism of rs3748093*A was significantly correlated with an increased risk of PTC in a Chinese population. Further investigation on the aetiological mechanism of PTC is needed to validate our results.