BRAFV600E mutation test on fine-needle aspiration specimens of thyroid nodules: Clinical correlations for 4600 patients

Abstract

Background: The BRAF^V600E mutation is valuable for the diagnosis, prognosis, and therapy of papillary thyroid cancer (PTC). However, studies related to this mutation have involved only a small number of patients. Therefore, we performed a large-scale analysis from a single institute to evaluate the accuracy of combined fine-needle aspiration (FNA) and BRAF^V600E mutation tests for PTC diagnosis.

Methods: A total of 4600 patients with thyroid nodules who underwent both FNA cytology and BRAF^V600E mutation analysis on FNA specimens were enrolled. The association between the BRAF^V600E mutation and clinicopathological features was analyzed. A separate analysis was performed for the 311 patients who underwent repeated FNA for comparison of cytological evaluation and BRAF^V600E mutation results. The diagnostic efficacy of the BRAF^V600E mutation test and cytologic diagnoses was evaluated for 516 patients who underwent preoperative FNA tests in comparison with conclusive postoperative histopathologic results.

Results: The cytology results of all 4600 FNA samples were categorized according to The Bethesda System for Reporting Thyroid Cytology (TBSRTC) stages I-VI, which accounted for 11.76%, 60.02%, 6.46%, 3.61%, 6.71%, and 11.43% of the samples, respectively. The BRAF^V600E mutation was detected in 762 (16.57%) FNA samples, with rates of 1.48%, 0.87%, 20.20%, 3.01%, 66.02%, and 87.81% for TBSRTC I-VI lesions, respectively. Among the 311 repeat FNA cases, 81.0% of the BRAF^V600E -positive and 4.3% of the BRAF^V600E -negative specimens with an initial indication of cytological non-malignancy were ultimately diagnosed as malignant by repeat FNA (p < 0.001). Among the 516 patients who underwent thyroidectomy, the sensitivity and specificity of the BRAF^V600E mutation test alone for PTC diagnosis were 76.71% and 100.0%, respectively, which increased to 96.62% and 88.03%, respectively, when combining the BRAF^V600E mutation test with cytology. BRAF^V600E mutation was significantly associated with lymph node metastasis (p < 0.001), but not with age, gender, or tumor size.

Conclusions: The BRAF^V600E mutation test in FNA samples has potential to reduce false negatives in PTC diagnosis, and therefore plays an important role in the diagnosis of thyroid nodules, especially those with an indeterminate or nondiagnostic cytology, which should be considered for repeat FNA.

Keywords: BRAFV600E mutation; cytology; fine-needle aspiration; thyroid nodules.

FIGURE 1

Typical case with thyroid solid nodules got repeated FNA with different cytological classification and response BRAF^V600E mutation results (A) Cytological sample from the initial FNA, Only a tiny clump of atypical cells are observed on the slide, it was subsumed as TBSRTC III: AUS (A1) and BRAF^V600E mutation was detected in the response sample (A2); (B) Cytological sample from the repeat FNA of the same case, a large number of lymphocytes and degenerative epithelioid cells (B2), several mass of cells showing as PTC cytologic features, such as enlarged, atypical nuclei with groove; intranuclear pseudoinclusions; and fine, granular chromatin (B1). (C) Histopathological examinations after thyroidectomy, one part of specimen show that the thyroid follicles was damaged with a large number of lymphocytes infiltrated and epithelioid cells degenerated (C1), another part of specimen show that typical papillary thyroid micro‐carcinoma with Hashimoto disease background (C2). BRAF, v‐raf murine sarcoma viral oncogene homolog B1; FNA, fine‐needle aspiration; PTC, papillary thyroid carcinoma; TBSRTC, The Bethesda System for Reporting Thyroid Cytopathology