UNLABELLED: Papillary thyroid carcinoma (PTC) is the most common malignancy of the thyroid gland. The high incidence of RET/PTC and Trk rearrangements or point mutations in RAS and c-MET oncogenes are the genetic hallmarks of PTC. Recently, oncogene BRAF has become a subject of great interest. The mutation of BRAF gene is characteristic for PTC and poorly differentiated and/or undifferentiated cancers derived from PTC. The predominant mutation of this gene, reported in PTC, is a single transversion in exon 15 (T1799A), which results in substitution of valine to glutamate at residue 600 (BRAF V600E, formerly position 1796 and residue V599E). It has been proved that the frequency of this mutation in PTC varies within the range of 29% to 69% in different populations.
OBJECTIVES: The aim of this study was to estimate the frequency of BRAF (V600E) mutation in PTC in the Polish population, and to evaluate the possible relationships between the presence of BRAF mutation and such parameters, as patient's age, gender, histopathological variant and the clinical staging of PTC.
METHODS: Analysis of BRAF (V600E) mutation was performed by single strand conformation polymorphism (SSCP) analysis and real-time allele-specific polymerase chain reaction (ASPCR) in tumour tissues from 25 patients with PTC. We compared the sensitivity of real-time AS-PCR, SSCP method and direct DNA sequencing of PCR products. We used 25 PTC tissues (including the follicular variant of PTC - 8 cases, the classic variant of PTC - 14 cases and the tall-cell variant of PTC - 3 cases).
RESULTS: V600E mutation in BRAF gene was detected in 12/25 (48%) cases of PTC. Mutation screening of exon 15 gene BRAF revealed three types of mutations, i.e. V600E, V600M, and overlapping mutations V600E/V600K. No correlation was found between BRAF mutation and patient's age and sex and particular stage in clinical staging systems (TNM Staging, the University of Chicago clinical class, and Ohio State University Staging). Regarding the histopathological variants of PTC, mutation in BRAF gene was more frequent in classic variant of PTC as compared with follicular variant of PTC.
CONCLUSION: The real-time AS-PCR method proved to be more sensitive than SSCP and sequencing of PCR products. Our study is the first one in which the frequency of BRAF (V600E) mutation in PTC was reported for the Polish population. Similarly to the results obtained by others, there was no coexistence of BRAF (V600E) mutation and RET/PTC and/or Trk rearrangements or RAS mutation in PTC tissue. Our results do not confirm the relationship between the BRAF (V600E) mutation and the clinical outcome of PTC.