"Glioma" is an umbrella. Underneath it are several distinct tumors that behave very differently. Knowing which type you or your child has is the key that unlocks the rest of your care.
Doctors sort gliomas in three overlapping ways: by the cell type they resemble, by grade (how fast they tend to grow), and — since 2021 — by molecular markers (specific gene changes inside the tumor). The major types include:
- Astrocytoma — arises from astrocyte-like cells. This is a broad family ranging from slower-growing tumors to aggressive ones. Whether the tumor carries an IDH mutation strongly shapes its outlook.
- Oligodendroglioma — defined by an IDH mutation together with a feature called 1p/19q codeletion. As a group, these tend to grow more slowly and respond better to treatment than many other gliomas.
- Glioblastoma — the most common and most aggressive glioma in adults. Under current rules, glioblastoma is specifically an IDH-wildtype (non-IDH-mutant) tumor.
- Ependymoma — arises from the cells lining the brain's fluid spaces and the spinal cord. It occurs in both children and adults and is graded and managed somewhat differently.
- Pediatric-type gliomas — children's gliomas are now recognized as biologically distinct from adult tumors and are classified separately, including pediatric low-grade gliomas and pediatric high-grade gliomas such as diffuse midline glioma.
The World Health Organization's 2021 classification reorganized brain tumors into groups that include adult-type diffuse gliomas, pediatric-type low-grade and high-grade gliomas, circumscribed astrocytic gliomas, and ependymal tumors. The practical takeaway for families is that your full diagnosis is usually several words long — a type, a grade, and one or more molecular markers — and each word carries meaning.
This blog is a map, not the territory. Each major type has its own dedicated article in this library with the detail it deserves.