PTEN and astrocytoma (excluding glioblastoma): In our series, low-grade astrocytomas are characterized with p53 and IDH1/2 mutations, consistent with known frequencies for this group [6]; whereas PTEN loss and EGFR amplification that facilitate survival signaling by the resulting constitutive activation of the PI3K pathway [40] were more represented in high-grade astrocytomas [6].