There are few studies on the molecular and genetic characteristics of gliomas in children. In adults, it has been reported that microsatellite instability is a predictive factor of the tumour response to irinotecan, because the defect in the DNA repair proteins results in a greater sensitivity to the drug. Furthermore, in adults, 30-40% of the high grade astrocytomas show MGMT promotor methylation and as a consequence the methylated tumours are more sensitive to the effect of alkylating drugs. Due to the lack of pediatric studies on MGMT promoter methylation and on microsatellites the question as to whether their determination has the same importance as in high grade glioma in adults cannot be answered.