Gliomas

Gliomas may be described as circumscribed or diffuse.

Circumscribed gliomas (e.g., pleomorphic xanthoastrocytoma, subependymal giant cell astrocytoma, pilocytic/pilomyxoid astrocytoma) have well-defined margins, and are generally considered benign. Maximal safe resection is the mainstay of treatment.

Diffuse astrocytomas (grade 2-4) represent a spectrum of the same highly infiltrative disease, with lower grades inevitably progressing to higher-grade lesions. They can be characterized on the basis of the isocitrate dehydrogenase (IDH) and histone 3 (H3) mutation status.

IDH-wildtype diffuse glioma (glioblastoma) is an aggressive primary brain tumor that presents in patients in the sixth or seventh decade of life. It is the most common type of glioma.

IDH-mutant gliomas (including oligodendroglioma, IDH-mutant, 1p/19q codeleted, grades 2-3; and astrocytoma, IDH-mutant, grades 2-4) tend to occur in young or middle-age patients.

H3 mutant gliomas (including diffuse midline glioma, H3 K27M altered; and diffuse hemispheric glioma, H3 G34-mutant) are aggressive (grade 4) brain tumors occurring in children, adolescents, and young adults.

There are no known predisposing factors for gliomas except for rare familial syndromes and prior cranial radiation therapy.

Treatments vary depending on tumor grade and molecular characteristics. Initial treatment typically includes maximal safe surgical resection, with the aim of gross total resection if possible. Adjuvant radiation therapy and chemotherapy is indicated for many diffuse gliomas, with regimens varying based on molecular pathology, extent of resection, and other patient-specific factors. Some patients deemed at lower risk for progression may defer initial systemic treatment and be managed with observation alone until progression occurs. Clinical trials or investigational therapies should be considered as the initial therapeutic option, as none of the available therapies are curative and prognosis is poor.

Gliomas are primary tumors of the brain arising from glial progenitor cells. Normal glia (astrocytes and oligodendrocytes) provide structural and metabolic support to the brain and neurons, regulate ion concentrations in the extracellular space, modulate synaptic transmissions, and take up and release neurotransmitters. Gliomas may be circumscribed or diffuse.