In both GGs and DNTs, the presence of BRAFV600E mutation was significantly associated with the expression of CD34, phosphorylated ribosomal S6 protein (pS6; marker of mTOR pathway activation) in dysplastic neurons and synaptophysin (P < 0.05).
Activation of the MAP Kinase (MAPK) pathway caused by the BRAFV600E mutation or the KIAA1549-BRAF fusion has been reported in pediatric GG and PA, respectively.
BRAFV600E mutation has been identified in up to 2/3 of pleomorphic xanthoastrocytomas (PXAs), World Health Organization grade II, as well as in varying percentages of PXAs with anaplastic features (PXA-A), gangliogliomas, extracerebellar pilocytic astrocytomas, and, rarely, giant cell glioblastoma multiforme (GC-GBMs).
In conclusion, DNT shared with PXA and GG, BRAF(V600E) mutation and/or CD34 expression, which represent molecular markers for these tumors, and we recommend searching for CD34 expression and BRAF(V600E) mutation in all DNT, especially the non-specific forms.
BRAFV600E mutation, a genetic abnormality seen in a significant percentage of pleomorphic xanthoastrocytomas and GGs, was assessed by polymerase chain reaction and identified in the tumor.
The highest frequencies of BRAF (V600E) mutations were found in WHO grade II pleomorphic xanthoastrocytomas (42/64; 66%) and pleomorphic xanthoastrocytomas with anaplasia (15/23; 65%), as well as WHO grade I gangliogliomas (14/77; 18%), WHO grade III anaplastic gangliogliomas (3/6) and pilocytic astrocytomas (9/97; 9%).
In the present study we searched for FGFR1-ITD by droplet digital PCR (DDPCR™) and for FGFR1 point mutations by HRM-sequencing in a series of formalin-fixed paraffin-embedded (FFPE) LGNTs including 12 DNT, 2 oligodendrogliomas lacking IDH mutation and 1p/19q co- deletion (pediatric-type oligodendrogliomas; PTOs), 3 pediatric diffuse astrocytomas (PDAs), 14 gangliogliomas (GGs) and 5 pilocytic astrocytomas (PAs).
It is recognized that IDH mutation negative, low-grade epilepsy associated tumors (LEAT) can show diffuse growth patterns and lack the diagnostic hallmarks of either classical dysembryoplastic neuroepithelial tumors (DNT) or typical ganglioglioma.
Their tumors showed distinctive features of ganglioglioma with low Ki-67 index (2%-4%), positive for the BRAF<sup>V600E</sup> mutation, but negative forIDH1/2 mutations.
SSCP analysis revealed an allelic variant of TSC2 to be significantly increased (exon 41: 50.0% vs controls 14%, P=0.0132), which previously was reported to be increased in gangliogliomas and mineralized focal cortical dysplasia as well.
Recent data suggest several components of the insulin-pathway, including TSC1 and TSC2 mutated in tuberous sclerosis complex (TSC), to be altered in gangliogliomas and FCD with Taylor type balloon cells (FCD(IIb)).