Anaplastic oligodendroglioma

Anaplastic oligodendroglioma (WHO grade III oligodendroglioma) is a rare, malignant primary brain tumor that arises from oligodendrocytes, the cells responsible for producing the myelin sheath that insulates nerve fibers in the central nervous system. It is the higher-grade counterpart of oligodendroglioma (WHO grade II) and is characterized by increased cellularity, mitotic activity, microvascular proliferation, and/or necrosis. A hallmark molecular feature is the co-deletion of chromosomal arms 1p and 19q, along with IDH1 or IDH2 gene mutations, which are now required for diagnosis under the WHO 2016 and 2021 classification systems. Anaplastic oligodendroglioma most commonly affects adults, typically presenting between the ages of 40 and 60 years. The tumor predominantly occurs in the cerebral hemispheres, particularly the frontal and temporal lobes. Key symptoms depend on tumor location and may include seizures (often the presenting symptom), headaches, cognitive changes, personality alterations, focal neurological deficits such as weakness or speech difficulties, and signs of increased intracranial pressure. Some patients may have a history of a previously diagnosed lower-grade oligodendroglioma that has undergone malignant transformation. The current treatment approach typically involves maximal safe surgical resection followed by adjuvant radiation therapy and chemotherapy. The PCV regimen (procarbazine, lomustine/CCNU, and vincristine) has demonstrated significant survival benefit in clinical trials, particularly in tumors with 1p/19q co-deletion. Temozolomide is also widely used as an alternative chemotherapeutic agent. Compared to other high-grade gliomas such as glioblastoma, anaplastic oligodendroglioma with 1p/19q co-deletion carries a relatively more favorable prognosis, with median overall survival often exceeding 10 years with appropriate treatment. However, the disease remains incurable, and recurrence is common, necessitating ongoing surveillance and potential additional treatments.

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