EGFR and anaplastic astrocytoma: The Fisher exact test revealed that the frequency of PTEN and EGFR alterations was significantly higher in higher grade tumors (GBM) in comparison to anaplastic astrocytoma (82% vs 25%, p = 0.007 for PTEN and 54.5% vs. 12.5%, p = 0.047 for EGFR).