MGMT and glioblastoma: A higher amplitude of the methylation signal was detected in the low grade and anaplastic glioma samples that may simply reflect the fact that in non-glioblastoma usually both MGMT copies are present, while in glioblastoma only one is methylated and the other one is lost due to the characteristic high frequency of deletions of chromosome 10 that reached 90 % in the M-GBM samples [22].