Evaluation of molecular diagnostic approaches for the detection of BRAF p.V600E mutations in papillary thyroid cancer: Clinical implications

Detection of BRAF V600E in Fine-Needle Aspiration Samples of Thyroid Nodules by Droplet Digital PCR

BACKGROUND

BRAF exon 15 p.V600E (BRAF V600E) mutation has been established as an important molecular marker for papillary thyroid carcinoma diagnosis by ultrasound-guided fine-needle aspiration biopsy (FNAB). Sanger sequencing is the gold standard for detecting BRAF V600E mutations but fails to identify low-frequency mutations. However, droplet digital PCR (ddPCR) is a popular new method for detecting low-frequency mutations. Here, we compare the efficiency of droplet digital PCR (ddPCR) and Sanger sequencing for detection of the BRAF V600E mutation in thyroid fine-needle aspiration (FNA) samples.

METHODS

Thyroid fine-needle aspiration samples from 278 patients with 310 thyroid nodules were collected. Sanger sequencing and ddPCR were conducted to detect the BRAF V600E mutation.

RESULTS

The BRAF V600E mutation was found in 94 nodules (30.32%) by ddPCR and 40 nodules (12.90%) by Sanger sequencing in 310 FNA samples. A total of 119 nodules were confirmed PTC by postsurgical pathology. Among which the BRAF mutation was found in 80 (67.23%) nodules by ddPCR and 31 (26.05%) by Sanger sequencing. All nodules carrying the mutation detected by Sanger sequencing (SS+) were verified by ddPCR (ddPCR+). Also, all nodules with no mutation detected by ddPCR were interpreted as wild-type by Sanger sequencing (SS-). In addition. Almost all SS+/ddPCR + nodules (95.00%; 38/40) and SS-/ddPCR + nodules (100.00%; 54/54) displayed a BRAF mutation rate of >5% and <15%, respectively, indicating easy misdetection by Sanger sequencing when the mutation rate is between 5 and 15%.

CONCLUSION

ddPCR has higher sensitivity than Sanger sequencing and we propose ddPCR as a supplement to Sanger sequencing in molecular testing of BRAF using FNAB samples.

Relationship between serum NDRG3 and papillary thyroid carcinoma

BACKGROUND

In recent years, papillary thyroid carcinoma is considered to be one of the fastest increaseing cancer. NDRG family member 3 (NDRG3) has been proposed as a molecular marker of tumor, and is expected to be used in clinic.

METHODS

Enzyme-linked immunosorbent assay was used to detect the serum NDRG3 expression in 81 papillary thyroid carcinoma cases, 75 benign thyroid nodules cases and 77 healthy control cases, respectively. Electrochemiluminescence method was applied to measure the levels of triiodothyronine, tetraiodothyronine, thyrotropin, thyroglobulin antibody and thyroid peroxidase antibody. Immunohistochemical staining was used to detect the expression of NDRG3 in papillary thyroid carcinoma, benign thyroid nodules and normal tissues adjacent to cancer.

RESULTS

The expression of serum triiodothyronine, tetraiodothyronine, thyrotropin, thyroglobulin antibody and thyroid peroxidase antibody and NDRG3 were significantly different among benign thyroid nodules, papillary thyroid carcinoma cases and healthy control groups (P <0.001). Only the expression of serum NDRG3 was significantly different between benign thyroid nodules and papillary thyroid carcinoma groups (P <0.001). Immunohistochemistry showed that NDRG3 was expressed in all three groups, the lowest in papillary thyroid carcinoma, the second in benign thyroid nodules, and the highest in normal tissues adjacent to cancer. Logistic regression analysis showed that serum NDRG3 was an independent protective factor for papillary thyroid carcinoma (OR =0.964, 95%CI =0.953 to 0.974, P <0.001). The ROC curve of non-papillary thyroid carcinoma diagnosed by serum NDRG3 showed the optimal cut-off value of 481.38 pg/ml, sensitivity of 72.4%, specificity of 90.1%, and the maximum area under the curve (AUC =0.902, 95%CI =0.863 to 0.940, P <0.001). The ROC curve of benign thyroid nodules diagnosed by serum NDRG3 showed the optimal critical value of 459.28 pg/ml, sensitivity of 81.3%, and specificity of 74.1% (AUC =0.863, 95%CI =0.808 to 0.919, P <0.001). The expression level of serum NDRG3 was significantly correlated with extrathyroid extensionand (P =0.007) and lymphatic metastasis of papillary thyroid carcinoma (P =0.019).

CONCLUSIONS

The decrease of NDRG3 expression can not only differential diagnosis benign thyroid nodules and papillary thyroid carcinoma, but also serve as a molecular marker for the diagnosis of papillary thyroid carcinoma.

Snail-1 Overexpression Correlates with Metastatic Phenotype in BRAFV600E Positive Papillary Thyroid Carcinoma

The ability of cancer to metastasize is regulated by various signaling pathways, including transforming growth factor β (TGFβ), also implicated in the upregulation of Snail-1 transcription factor in malignant neoplasms. B-type Raf kinase gene (BRAF)V600E, the most common driving mutation in papillary thyroid carcinoma (PTC), induces epithelial to mesenchymal transition (EMT) in thyroid cancer cells through changes in the Snail-1 level, increasing cell migration and invasion. However, little is known about the mechanism of Snail-1 and BRAFV600E relations in humans. Our study included 61 PTC patients with evaluated BRAFV600E mutation status. A total of 18 of those patients had lymph node metastases-of whom 10 were BRAFV600E positive, and 8 negative. Our findings indicate that the expression of Snail-1, but not TGFβ1, correlates with the metastatic phenotype in PTC. This is the first piece of evidence that the upregulation of Snail-1 corresponds with the presence of BRAFV600E mutation and increased expression of Snail-1 in metastatic PTC samples is dependent on BRAFV600E mutation status.

Microfluidic Droplet Digital PCR Is a Powerful Tool for Detection of BRAF and TERT Mutations in Papillary Thyroid Carcinomas

We examined the utility of microfluidic digital PCR (dPCR) for detection of BRAF and TERT mutations in thyroid tumors. DNA extracted from 100 thyroid tumors (10 follicular adenomas, 10 follicular cancers, 5 medullary cancers, and 75 papillary thyroid cancer (PTC) were used for detection of BRAF and TERT mutations. Digital PCRs were performed using rare mutation SNP genotyping assays on QuantStudio 3D platform. In PTCs, BRAFV600E was detected by dPCR and Sanger sequencing in 42/75 (56%) and in 37/75 (49%), respectively. BRAFV600E was not detected in other tumors. The ratio of mutant/total BRAF alleles varied from 4.7% to 47.5%. These ratios were higher in classical PTCs (27.1%) as compared to follicular variant PTCs (9.4%) p = 0.001. In PTCs with and without metastases, the ratios of mutant/total BRAF alleles were 27.6% and 18.4%, respectively, (p = 0.03). In metastatic lesions percentages of mutant/total BRAF alleles were similar to those detected in primary tumors. TERTC228T and TERTC250T were found in two and one cases, respectively, and these tumors concomitantly harbored BRAFV600E. These tumors exhibited gross extra-thyroidal extension, metastases to lymph nodes, and pulmonary metastases (one case). Our results showed that dPCR allows quantitative assessment of druggable targets in PTCs and could be helpful in a molecular-based stratification of prognosis in patients with thyroid cancer.

BRAF mutation analysis by ARMS-PCR refines thyroid nodule management

BACKGROUND

Fine-needle aspiration (FNA) of thyroid nodules leads to nearly 25% indeterminate nodules, while BRAF^V600E mutation helps to predicting papillary thyroid carcinoma (PTC). However, the clinical validity and utility of the BRAF^V600E mutation detected using preoperative FNA samples in a large cohort were rarely reported.

AIM

To explore the clinical significance of the BRAF^V600E mutation on preoperative diagnosis and decision-making in a large FNA cohort in China.

DESIGN

This was a prospective study of BRAF^V600E mutation analysis using an amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) in FNA samples.

PATIENTS

The study involved 2640 samples from 2307 patients undergoing FNA procedures in a Chinese medical centre.

RESULTS

A high mutation rate of 86.7% was found in the PTC population. For indeterminate thyroid nodules, the malignant rate of BRAF^V600E+ and BRAF^V600E- was 87.8% and 39.5% in the Bethesda System for Reporting Thyroid Cytopathology (BSRTC) III, and 88.2% and 31.8% in the BSRTC IV, respectively. A cost-effective diagnostic model combining both BSRTC grading and BRAF^V600E mutation status showed the highest sensitivity of 82.9% and specificity of 85.4%. Central lymph node metastasis (CLNM) was independent of the BRAF mutation status and accounted for 34.2% of the patients with PTC. C_T values of BRAF^V600E of patients with PTMC were significantly lower in young patients and patients with CLNM.

CONCLUSIONS

The combined analysis of cytological results and BRAF^V600E mutation is highly recommended in BRAF^V600E high-prevalence regions, including China. Prophylactic central neck dissection should be performed in selected patients without regard to the BRAF mutation status.

Coexisting Germline CHEK2 and Somatic BRAFV600E Mutations in Papillary Thyroid Cancer and Their Association with Clinicopathological Features and Disease Course

BRAF^V600E is the most common somatic mutation in papillary thyroid carcinoma (PTC) and the majority of evidence indicates that it is associated with an aggressive clinical course. Germline mutations of the CHEK2 gene impair the DNA damage repair process and increase the risk of PTC. Coexistence of both mutations is expected to be associated with poorer clinical course. We evaluated the prevalence of concomitant CHEK2 and BRAF^V600E mutations and their associations with clinicopathological features, treatment response, and disease course in PTC patients. The study included 427 unselected PTC patients (377 women and 50 men) from one center. Relationships among clinicopathological features, mutation status, treatment response, and disease outcomes were assessed. Mean follow-up was 10 years. CHEK2 mutations were detected in 15.2% and BRAF^V600E mutations in 64.2% patients. Neither mutation was present in 31.4% cases and both BRAF^V600E and CHEK2 mutations coexisted in 10.8% patients. No significant differences in clinicopathological features, initial risk, treatment response, or disease outcome were detected among these patient groups. CHEK2 mutations were significantly associated with older age, while BRAF^V600E was significantly associated with older age and extrathyroidal extension. The coexistence of both mutations was not associated with more aggressive clinicopathological features of PTC, poorer treatment response, or disease outcome.

[Tumors of the thyroid gland. Proposal for the management and study of samples from patients with thyroid neoplasms]

The recent changes in the classification and staging of thyroid tumors have arisen from the need to provide an adequate response to the exponential increase of thyroid cancer, which, however, has not been accompanied by an increase in mortality. These changes pretend to reduce overdiagnoses of malignancy, unnecessary treatment, side effects as well as cost for the health system. To this end, this article reviews recommendations for the management of thyroid surgical pathology samples with emphasis on the new terminology of the WHO classification. The basic criteria for the diagnosis of malignancy in well-differentiated thyroid carcinomas are reviewed and the criteria for NIFTP (non-invasive follicular tumor with papillary-like nuclear features) diagnosis are updated. Recommendations for the elaboration of the pathological report are also included.

Immunohistochemistry cannot replace DNA analysis for evaluation of BRAF V600E mutations in papillary thyroid carcinoma

INTRODUCTION

The BRAF V600E mutation is the most common genetic event occurring in papillary thyroid cancer (PTC). Recently, the possibility of using immunohistochemistry (IHC) to detect the BRAF V600E mutation has been reported.

MATERIALS AND METHODS

In 140 patients with classical PTC, the status of the BRAF V600E mutation was determined by IHC (using two alternative staining protocols, IHC-1 and IHC-2) and molecular biology methods: Sanger sequencing (SEQ) and real-time PCR (qPCR).

RESULTS

The BRAF V600E mutation was detected in 57.1% (80/140) patients by IHC-1 and 62.9% (88/140) patients by IHC-2. The highest correlation in detecting the BRAF V600E mutation was found between IHC-2 and qPCR (94.2%), and between IHC-1 and qPCR (83.9%). Correlations between IHC-1 and SEQ and between IHC-2 and SEQ were 71.5% and 76.2%, respectively. The IHC-2 protocol had higher sensitivity, PPV, and NPV, and Cohen's kappa than IHC- 1. The presence of BRAF V600E mutation in IHC-2 statistically correlated with age at diagnosis, histopathological stage, and extrathyroidal extension.

CONCLUSIONS

The results obtained in this study indicate a lack of concordance between BRAF V600E detection by IHC and molecular methods. The IHC method cannot replace molecular methods for the detection of the BRAF V600E mutation.