Objective: The p.V600E BRAF and RAS mutations are found in 30-80% of differentiated thyroid carcinoma (DTC). BRAF mutation has been associated with poor prognosis. This study investigated the role of molecular studies in preoperative diagnosis of DTC and the association of p.V600E mutation with prognostic factors.
Design: Prospective study.
Methods: A total of 202 patients with cytological diagnosis of Bethesda III-VI underwent preoperative molecular studies and subsequent thyroidectomy. p.V600E and RAS mutations were studied in the cytology smears, using real-time PCR genotyping technique. The BRAF mutation (BRAF(+) or BRAF(-)) was correlated with histological and clinical findings.
Results: Molecular study of 172 nodules with Bethesda III-V cytology improved negative predictive value and accuracy of Bethesda III and IV diagnosis. BRAF mutation was present in 65% of 94 DTC and p.Q61R NRAS in one. Except for age, BRAF(+) and BRAF(-) did not differ in sex, tumor size, histological subtype, multifocality, vascular invasion, extrathyroidal extension, or prognostic staging. Among papillary carcinomas, lymph node (LN) metastasis was diagnosed in 23% BRAF(+) and 37% BRAF(-). Distant metastasis occurred in four BRAF(-). Recurrent or persistent disease was more frequent in BRAF(-) (26.7 vs 3.3% BRAF(+), P=0.002) along follow-up of 29.8±10 months. BRAF(+) patients without LN metastasis by pre-operative evaluation submitted to thyroidectomy with central neck dissection (CND) had more frequent LN metastasis (45 vs 5% no CND, P=0.002), but no difference in clinical outcome was observed.
Conclusions: Pre-operative identification of BRAF mutation improved cytological diagnosis of DTC, but it was not associated with poor prognostic factors. Prophylactic CND did not guarantee better outcome in BRAF(+) patients.