The BRAF(V600E) mutation in papillary thyroid microcarcinoma: does the mutation have an impact on clinical outcome?

Context: An activating mutation in the gene BRAF has been correlated with poorer prognosis and more aggressive clinical course in papillary thyroid carcinoma (PTC). We therefore hypothesized that the good prognosis, high 5-year disease-free rate and high survival rate of patients with less aggressive papillary thyroid microcarcinoma (pT1aNo-x) would be associated with a lower incidence of the BRAF(V600E) mutation.

Objectives: To evaluate the frequency of the activating mutation BRAF(V600E) in low-risk papillary thyroid microcarcinoma (pT1aNo-x at the moment of diagnosis) and the association of the mutation with the clinical outcome in a retrospective analysis.

Study design: BRAF(V600E) was characterized in 113 PTC patients diagnosed with pT1aNo-x (one PTC focus with a diameter <1 cm, without lymph node or distant metastases according to IUCC/AJCC TNM staging system 2010). Genotyping was performed on DNA extracted from thyroid tumour tissue using direct capillary sequencing, and allele-specific amplification PCR was used to resolve equivocal results. Retrospective analysis of the clinical course of PTC was then correlated with BRAF status in the primary tumour tissue.

Results: The BRAF(V600E) mutation was detected in 78 of the 113 pT1aNo-x patients (69·0%). We observed no persistence, locoregional recurrence, lymph node or distant metastases or deaths in the study group during the 12-year study (January 2001 to December 2012).

Conclusions: The presence of the activating BRAF(V) (600E) mutation in a significant percentage of papillary thyroid microcarcinoma indicates that further analyses are required to verify its usefulness as a predictor of clinical outcome in PTC. In this study, there was no correlation between BRAF-positive primary focus of papillary microcarcinoma and more aggressive or recurrent disease.