1p/19q Deletions for Glioma

Testing for 1p and 19q deletions in glial brain tumors, specifically oligodendrogliomas, has diagnostic and prognostic value. Whole-arm deletions of chromosomes 1p and 19q (with concurrent IDH1 or IDH2 mutation) are diagnostic for oligodendroglioma according to WHO classification. Co-deletion of both the 1p and 19q regions in adult oligodendroglioma patients is associated with improved response and longer survival in patients receiving radiation and/or chemotherapy. Results can help distinguish the oligodendroglioma subtype of diffuse gliomas from astrocytomas and from other tumor types with similar morphology such as clear cell ependyomas, central or extraventricular neurocytomas, and dysembryoplastic neuroepithelial tumors (DNETs). Partial deletions may be seen in high-grade glioblastomas. Polysomy in the presence of whole-arm co-deletions may occur in anaplastic oligodendrioglioma.