Oligodendroglioma, IDH-mutant and 1p/19q-codeleted

Oligodendroglioma, IDH-mutant and 1p/19q-codeleted

• Definition: A diffusely infiltrating glioma with IDH1 or IDH2 mutation and codeletion of chromosome arms 1p and 19q (CNS WHO grade 2 or 3)

ICD-O Coding

• 9450/3: Oligodendroglioma, IDH-mutant and 1p/19q-codeleted, grade 2
• 9451/3: Oligodendroglioma, IDH-mutant and 1p/19q-codeleted, grade 3

ICD-11 Coding

• 2A00.0Y & XH7K31: Other specified gliomas of brain & Oligodendroglioma, IDH-mutant and 1p/19q-codeleted

Localization

• 59% of oligodendrogliomas are located in the frontal lobe, 14% in the temporal lobe, 10% in the parietal lobe, and 1% in the occipital lobe
• 62% of CNS WHO grade 3 oligodendrogliomas are frontal tumors, 16% are temporal, 15% are parietal, and 6% are occipital

Genetic Profile

• Entity-defining alterations: missense mutations affecting IDH1 codon 132 or IDH2 codon 172 combined with whole-arm deletions of 1p and 19q
• Over 90% of IDH mutations in oligodendrogliomas correspond to the canonical IDH1 p.R132H mutation
• The 1p/19q codeletion is caused by an unbalanced translocation between chromosomes 1 and 19, resulting in loss of the der(1;19) (p10;q10) chromosome
• TERT promoter hotspot mutations are present in the vast majority of IDH-mutant and 1p/19q-codeleted oligodendrogliomas

Germline Mutations

• Familial oligodendrogliomas have been associated with germline mutations of POT1, a shelterin complex gene
• Cases of familial oligodendroglioma with 1p/19q codeletion have been reported
• Variants in or near the D2HGDH gene, which codes for D-2-hydroxyglutarate dehydrogenase, have been associated with IDH-mutant gliomas
• rs111976262, located near the FAM20C gene, has been associated with IDH-mutant, TERT promoter-mutant, and 1p/19q-codeleted oligodendrogliomas