Astrocytomas are tumors that arise from astrocytes, the star-shaped support cells of the brain. They are one of the most common glioma families, and they span a wide range of behavior.
The biggest dividing line in adult astrocytomas is IDH status. An astrocytoma, IDH-mutant is now treated as a single tumor type that is then graded 2, 3, or 4. As a group, IDH-mutant astrocytomas tend to occur in younger adults and behave less aggressively than glioblastoma — though grade still matters, and they require careful, often lifelong follow-up. By contrast, an aggressive IDH-wildtype astrocytic tumor in an adult is generally classified as glioblastoma and is covered in its own article.
A few features patients commonly hear about:
- Grade ranges from 2 (slower-growing but infiltrative) to 4 (aggressive). Importantly, an IDH-mutant astrocytoma can be graded 4 based on a specific gene change (CDKN2A/B deletion) even without the classic aggressive appearance.
- Diffuse means the tumor's edges blend into normal brain rather than forming a clean ball — which is why complete surgical removal can be difficult.
- Circumscribed astrocytomas, such as pilocytic astrocytoma, are a separate, more contained category, often grade 1, common in children, and sometimes curable with surgery alone.
What to expect depends on grade, IDH status, location, and how much can be safely removed. Treatment often combines surgery (to remove as much as is safe and to obtain tissue), and depending on the situation, radiation, chemotherapy, or — for certain IDH-mutant grade 2 tumors after surgery — targeted therapy with vorasidenib. The American Brain Tumor Association and National Cancer Institute both emphasize that astrocytoma is not one disease, and that molecular testing is now essential to know exactly which astrocytoma you are dealing with.