In a subset of cases (two GBM and two ODGs), 1p/19q status was also confirmed by array-CGH. Array-CGH analysis was performed using 180 mer oligonucleotide probe technology (SurePrint G3 Human CGH 4 × 180K, Agilent Technologies, Santa Clara, CA, USA), according to the manufacturer's instructions. Raw data were generated using Agilent Feature Extraction and analyzed using Cytogenomics 3.0.4.1, with the ADM-2 algorithm (Agilent Technologies, Santa Clara, CA, USA). To improve the accuracy of the results, the Diploid Peak Centralization algorithm was also applied.
The aberration filter was set to detect a minimum of five consecutive probes/region, and the minimum absolute average log ratio (MAALR) was ± 0.25. A second analysis was run with a MAALR of ± 0.15 (again with a minimum number of five probes/region), to detect low level of mosaicism. Only copy number variants not already reported in the public database of genomic variants (http://projects.tcag.ca/variation/ ) were listed. Genomic coordinates are according to the build 37 assembly (March 2009) of the Human Genome Reference consortium (GRch37/hg19).
The aberration filter was set to detect a minimum of five consecutive probes/region, and the minimum absolute average log ratio (MAALR) was ± 0.25. A second analysis was run with a MAALR of ± 0.15 (again with a minimum number of five probes/region), to detect low level of mosaicism. Only copy number variants not already reported in the public database of genomic variants (