Clinical Utility of BRAF, NRAS, and TERT Promoter Mutation in Preoperative Thyroid Fine-Needle Aspiration Biopsy: A Diagnostic Study From Dharmais Cancer Hospital

Abstract

Molecular testing of thyroid nodules becomes important for improving the accuracy of fine-needle aspiration biopsy (FNAB). This study aimed to investigate the diagnostic utility of BRAF, NRAS, and TERT promoter mutation in thyroid nodules at Dharmais Cancer Hospital.<br />Methods: We performed a prospective diagnostic study involving 50 patients with thyroid nodules who needed surgery between September 2013 and August 2014. Mutational hotspots in BRAF exon 15, NRAS exon 3, and TERT promoter region were analyzed by Sanger sequencing from FNAB specimens. Cytology and molecular data were compared to histopathology results.<br />Result: Of the 50 cases included in the analysis, 39 cases (78%) were thyroid malignancies. Mutations of BRAF, NRAS, and TERT promoter were detected in 31% (12/39), 18% (7/39), and 13% (5/39) cases, respectively. BRAF and NRAS mutations were found mutually exclusive, while all of TERT promoter mutation was found coexistent either with BRAF (40%) or NRAS (60%). The combination of FNAB cytology and molecular testing resulted in 69% sensitivity, 100% specificity, 100% positive predictive value, 48% negative predictive value, and 76% accuracy.<br />Conclusion: Molecular testing of BRAF, NRAS, and TERT mutations improve the sensitivity of thyroid FNAB and is beneficial for more definitive treatment in selective cases. However, the NPV is relatively low to avoid the need for diagnostic surgery. Therefore, further studies to identify more sensitive methods and more comprehensive molecular markers in the diagnosis of thyroid nodules are needed.

Keywords: Diagnostic; Thyroid cancer; fine-needle aspiration biopsy; hotspot mutation.

Figure 1

Patients Inclusion Flowchart for Mutation Analysis

Figure 2

Representative Sequencing Results for BRAF, NRAS, and TERT Promoter Mutation. (A) Sequence of wildtype BRAF exon 15, codon 600 (GTG, arrow). (B) Sequence of mutant BRAF exon 15, codon 600, showing overlapping peak (GTG>GAG, arrow) indicated substitution of amino acid valine to glutamic acid. (C) Sequence of wildtype NRAS exon 3, codon 61 (CAA, arrow). (D) Sequence of mutant NRAS exon 3, codon 61, showing overlapping peak (CAA>CGA, arrow) indicated substitution of amino acid glutamine to arginine. (E) Sequence of wildtype TERT promoter (CTCCGG, arrow). (F) Sequence of mutant TERT promoter, showing overlapping peak at nucleotide base position number 1,295,228 (228C>T, arrow)

Figure 3

Mutation Status of FNAB Specimens. The thyroid nodules are categorized based on cytology results as malignant, indeterminate, and benign. *FNAB, fine needle aspiration biopsy; AC, anaplastic carcinoma; PDTC, poorly differentiated thyroid carcinoma; PTCcv, papillary thyroid carcinoma classic variant; PTCfv, papillary thyroid carcinoma follicular variant