Objective: The somatic point mutation in the BRAF gene, which results in a valine-to-glutamate sub-
stitution at residue 600 (BRAF
V600E
), is an ideal hallmark of papillary thyroid carcinoma (PTC). How-
ever, its prevalence is varyingly reported in different studies, and its expression in the follicular variant
PTC is controversial, reducing its potential usefulness as diagnostic marker.
Design and methods: We developed an assay based on mutant allele-specific PCR amplification (MASA)
to detect BRAF mutation. We compared the sensitivity of MASA, single-strand conformation poly-
morphism (SSCP) and direct DNA sequencing of PCR products. Then, we used MASA 78 to analyze
78 archival thyroid tissues, including normal samples, follicular adenomas, follicular carcinomas and
PTC.
Results: The MASA assay proved to be a more sensitive method than SSCP and DNA sequencing of
PCR products. BRAF mutation was found by MASA in 19/43 (44.2%) of PTC, including 14/31
(45.2%) classic forms and 5/12 (41.7%) follicular variants. No mutations of BRAF were detected
in the normal thyroid tissues, nor in follicular adenomas or follicular carcinomas. No correlation
was found between BRAF mutation and clinicopathologic features nor with recurrence during a post-
operative follow-up period of 4–11 years. BRAF
V600E
significantly correlated with absence of node
metastasis.
Conclusions: BRAF
V600E
is present in PTC, both in the classic form and in follicular variant with simi-
lar prevalence. No correlation was found between BRAF mutation and aggressive clinical behavior.
MASA-PCR proved to be a specific, sensitive and reliable method to detect BRAF T1799A in DNA
extracted from different sources, including cytologic samples obtained either fresh or from archival
glass slides. We propose this method as a useful tool to improve accuracy of preoperative diagnosis
identifying PTC from biopsies with indeterminate cytologic findings