IDH1 and central nervous system cancer: Recent advances in understanding of glioma subtypes (e.g. proneural, neural, mesenchymal) based on gene expression [20], somatic mutations (e.g. IDH1) [21] and global patterns of methylation (glioma CpG island methylator pheynotype; G-CIMP) [22] suggest there are important subgroups of glioma that may represent distinct pathological entities.