FGFR1 and pilocytic astrocytoma: While the RGNT, EVN, and DNT methylation clusters are composed of tumors with nearly universal FGFR1 alterations, the three pilocytic astrocytoma methylation clusters are composed of a mixture of tumors with alterations in various genes causing activation of the MAP kinase signaling pathway (e.g. BRAF, FGFR1, NF1, RAF1, KRAS) [7, 33, 36, 38].