MGMT and neoplasm: Our observation is in the same range as reports by Martinez et al., Blanc et al., Criniere et al., Cankovic et al. and Gonzalez-Gomez et al. who found that the majority of the methylated tumours also exhibited an unmethylated band, which may arise from either normal cells within the tumour sample or from a tumour cell side population.18,26,31,34,37 Our experience shows that MGMT promoter methylation testing may be technically challenging.