IDH1 and glioma: Somatic mutations in the isocitrate dehydrogenase genes IDH1 and IDH2 occur at high frequency in various tumour types including gliomas (primary malignant central nervous system tumours), intrahepatic cholangiocarcinomas (bile duct tumours), enchondromas and chondrosarcomas (bone tumours), sinonasal undifferentiated carcinomas and leukemias [12, 33].