oligodendroglioma

Oligodendroglioma is a type of glioma that arises from the oligodendrocyte lineage in the brain. It most commonly affects adults and typically develops in the cerebral hemispheres, especially the frontal lobes. Seizures are a common presenting symptom, and the tumor often grows slowly.

Pathology shows tumor cells with a characteristic fried-egg appearance and a delicate capillary network. Grades II and III (anaplastic) reflect increasing cellularity and mitotic activity. Modern diagnosis relies on combined histology and molecular features: tumors that harbor an IDH mutation and a 1p/19q codeletion are defined as oligodendrogliomas. ATRX expression is usually retained, and TP53 mutations are less common. MGMT promoter methylation may influence responsiveness to alkylating chemotherapy.

Diagnosis is established through tissue sampling (biopsy or resection) with subsequent molecular testing. Imaging aids planning but cannot substitute for molecular classification, and the current WHO CNS5 framework emphasizes the IDH mutation and 1p/19q codeletion status.

Treatment typically begins with maximal safe surgical resection. Postoperative radiotherapy is commonly used, and chemotherapy is often added, especially for higher-risk disease. The most effective systemic regimen for codeleted, IDH-mutant tumors is a PCV combination (procarbazine, lomustine, and vincristine); temozolomide may be used in some cases when PCV is not suitable. MGMT promoter methylation status can influence chemotherapy decisions.

Prognosis is relatively favorable compared with other diffusely infiltrating gliomas, particularly for tumors with both IDH mutation and 1p/19q codeletion. These tumors tend to respond well to therapy and show longer survival than non-codeleted or IDH-wildtype gliomas. Recurrence is common, necessitating long-term follow-up.