BRAFV600E MUTATION IN THE DIAGNOSIS OF UNICYSTIC AMELOBLASTOMA

Abstract

Unicystic ameloblastoma (UA) presents clinical and radiographic similarities with dentigerous and radicular cysts. The BRAFV600E activating mutation has been reported in a high proportion of ameloblastomas. The purpose of the study was to assess the utility of detection of the BRAFV600E mutation in the differential diagnosis of UA with dentigerous and radicular cysts. 26 archival samples were included, comprising 8 UA, 9 dentigerous and 9 radicular cysts. The mutation was assessed in all samples by anti-BRAFV600E (clone VE1) immunohistochemistry (IHC) and by TaqMan® mutation detection qPCR assay. Sanger sequencing was further carried out when samples showed conflicting results in the IHC and qPCR. Although all UA (8/8) showed positive uniform BRAFV600E staining, the mutation was not confirmed by qPCR and Sanger sequencing in 3 samples. Positive staining for the BRAFV600E protein was observed in 1 dentigerous cyst, but it was not confirmed by the molecular methods. Furthermore, 2/9 dentigerous cysts and 2/9 radicular cysts showed nonspecific immunostaining of the epithelium or plasma cells. None of the dentigerous or radicular cysts cases presented the BRAFV600E mutation in the qPCR assay. The BRAFV600E antibody IHC may show nonspecific staining, but molecular assays may be useful for the diagnosis of UA.