Comparison of diagnostic methods for detection of BRAFV600E mutation in ameloblastoma

Abstract

BackgroundAmeloblastoma is an aggressively growing, highly recurrent odontogenic jaw tumor. Its association with BRAFV600E mutation is an indication for BRAFV00E‐inhibitor therapy The study objective was to identify a sensitive low‐cost test for BRAFV600E‐positive ameloblastoma. We hypothesized that immunohistochemical staining of formalin‐fixed paraffin‐embedded tissues for BRAFV600E mutation is a low‐cost surrogate for BRAFV600E gene sequencing when laboratory resources are inadequate for molecular testing.MethodsTissues from 40 ameloblastoma samples were retrieved from either formalin‐fixed paraffin‐embedded blocks, RNAlater™ stabilization solution or samples inadvertently pre‐fixed in formalin before transfer to RNAlater™. BRAFV600E mutation was assessed by Direct Sanger sequencing, Amplification Refractory Mutation System‐PCR and immunohistochemistry (IHC).ResultsBRAFV600E mutation was detected by IHC, Amplification Refractory Mutation System‐PCR and Direct Sanger sequencing in 93.33%, 52.5% and 30% of samples respectively. Considering Direct Sanger sequencing as standard BRAFV600E detection method, there was significant difference between the three detection methods (𝜒2 (2) = 31.34, p < 0.0001). Sensitivity and specificity of IHC were 0.8 (95% CI: 0.64–0.90) and 0.9 (95% CI: 0.75–0.99) respectively, while positive predictive value and negative predictive value (NPV) were 0.9 and 0.8 (Fischer's test, p < 0.0001) respectively. Sensitivity and specificity of Amplification Refractory Mutation System‐PCR detection method were 0.7 (95% CI: 0.53–0.80) and 0.9 (95% CI = 0.67–0.98) respectively, while PPV and NPV were 0.9 and 0.6 respectively (Fischer's test, p < 0.0001).ConclusionLow‐cost and less vulnerability of IHC to tissue quality make it a viable surrogate test for BRAFV600E detection in ameloblastoma. Sequential dual IHC and molecular testing for BRAFV600E will reduce equivocal results that could exclude some patients from BRAFV600E‐inhibitor therapies.

Malignant transformation of primary ameloblastoma of skull: case report and review of current literature

“…Molecularly targeted therapy research is focused on BRAF mutations, as 63% to 82% of AM patients and 38% of AMCa patients have BRAF V600E mutations ( 9 , 20 – 24 ).And most of them are located in the mandible and are sensitive to targeted drugs such as vemurafenib. BRAF-V600E mutations have also been found to be associated with aggressive behavior in AMCa, which can be accurately diagnosed by immunohistochemistry, which can be used to assess prognosis and select treatment ( 12 , 15 , 24 – 27 ). A small number of studies have found that SMO-mutated AM are predominantly located in the maxilla, however, more clinical studies are needed to overcome resistance to targeted drugs and reduce adverse effects ( 12 , 24 , 28 ).…”