glioma

Glioma is a type of tumor that arises from glial cells in the brain or spinal cord. Glial cells provide support and insulation for neurons. Gliomas are the most common primary brain tumors in adults and can be diffuse or focal. They originate mainly from astrocytes, oligodendrocytes, or ependymal cells and tend to infiltrate surrounding brain tissue.

The World Health Organization classifies gliomas into four grades (I–IV) based on histology and, more recently, molecular features. Low-grade tumors (grade I–II) tend to grow slowly, while high-grade tumors (grade III–IV) are more aggressive. The most aggressive glioma is glioblastoma, a grade IV tumor that often shows rapid progression and marked invasiveness. Molecular markers such as IDH mutation status and 1p/19q co-deletion, along with MGMT promoter methylation, are increasingly used to refine classification and prognosis. IDH-mutant oligodendrogliomas and certain astrocytomas have different treatment responses and outcomes compared with IDH-wildtype tumors.

Clinical presentation depends on the tumor’s location and size, commonly including headaches, seizures, focal neurological deficits, or cognitive changes. Diagnosis relies on magnetic resonance imaging with contrast, followed by tissue diagnosis from biopsy or surgical resection. Imaging may show ring-enhancing or infiltrative patterns, especially in glioblastoma. Treatment typically starts with maximal safe surgical resection when feasible, followed by radiotherapy. Concurrent and adjuvant chemotherapy (often temozolomide) is standard for higher-grade tumors. Recurrent disease may be managed with additional surgery, reirradiation, chemotherapy, or novel therapies such as tumor treating fields.

Prognosis varies widely. Glioblastoma carries a poor median survival of about 12–15 months with current standard therapy, whereas low-grade gliomas can have longer survival, particularly with favorable molecular profiles. Risk factors include prior ionizing radiation and certain genetic syndromes.