Pilocytic astrocytoma (PA) is the most common glioma in pediatric patients and 
occurs in different locations. Chromosomal alterations are mostly located at 
chromosome 7q34 comprising the BRAF oncogene with consequent activation of the 
mitogen-activated protein kinase pathway. Although genetic and epigenetic 
alterations characterizing PA from different localizations have been reported, 
the role of epigenetic alterations in PA development is still not clear. The aim 
of this study was to investigate whether distinctive methylation patterns may 
define biologically relevant groups of PAs. Integrated DNA methylation analysis 
was performed on 20 PAs and 4 normal brain samples by Illumina Infinium 
HumanMethylation27 BeadChips. We identified distinct methylation profiles 
characterizing PAs from different locations (infratentorial vs supratentorial) 
and tumors with onset before and after 3 years of age. These results suggest 
that PA may be related to the specific brain site where the tumor arises from 
region-specific cells of origin. We identified and validated in silico the 
methylation alterations of some CpG islands. Furthermore, we evaluated the 
expression levels of selected differentially methylated genes and identified two 
biomarkers, one, IRX2, related to the tumor localization and the other, TOX2, as 
tumoral biomarker.