Peptide nucleic acid clamp polymerase chain reaction reveals a deletion mutation of the BRAF gene in papillary thyroid carcinoma: A case report

The BRAF point mutation is the most common genetic event in papillary thyroid carcinoma (PTC), occurring in 29-69% of such tumors. The V600E mutation accounts for up to 95% of all BRAF mutations. Therefore, the majority of diagnostic assays have been developed to detect only the V600E mutation of the BRAF gene. A peptide nucleic-acid (PNA)-clamp quantitative polymerase chain reaction (qPCR) was developed to detect the V600E mutation and other mutations in the BRAF gene. In this study, a 3-bp deletion mutation (c.1799_ 1801delTGA) was detected in a subject with a PTC by PNA clamp qPCR, in contrast with the results of allele-specific (AS)-PCR. The mutant allele was not detected by AS-PCR, but was detected using PNA-clamp PCR. The atypical 3-bp deletion mutation (c.1799_1801delTGA) was identified by confirmatory PCR combined with sequencing. The conversion of codons 600 (GTG) and 601 (AAA) into a single codon (GAA) resulted in the insertion of a glutamic acid residue into the activation segment of the B-raf protein (p.V600_K601delinsE). In cases where PTC is highly suspected but no mutation is detected by AS-PCR specific for V600E, PNA clamp qPCR, which is complementary to other sequencing methods, should be performed in order to detect other mutations in the BRAF gene.