IDH-wildtype (tumor designation)

What it is

"IDH-wildtype" is the designation for a glioma that does not carry an IDH mutation. Among adult diffuse astrocytic gliomas, being IDH-wildtype (with certain additional features) defines glioblastoma — the most aggressive type — and these tumors generally follow a more aggressive course.

Understanding IDH-wildtype (tumor designation)

When a diffuse astrocytic glioma in an adult is found to be IDH-wildtype, it generally falls into the glioblastoma category, including tumors that meet specific molecular criteria (TERT promoter mutation, EGFR amplification, or combined chromosome 7 gain and 10 loss) even without the most aggressive appearance. IDH-wildtype gliomas typically affect older adults and grow more aggressively than IDH-mutant gliomas, which is why this designation carries a more guarded prognosis. (In children, gliomas are classified by their own molecular features rather than IDH status.) Because the IDH-wildtype designation has major implications, IDH testing is essential to distinguish it from the more favorable IDH-mutant tumors. Understanding the IDH-wildtype designation clarifies what it means and why it defines the most aggressive adult glioma.

Why it matters

Understanding the IDH-wildtype designation helps patients and families see that the absence of an IDH mutation, in adult diffuse astrocytic tumors, defines glioblastoma and a more aggressive course — which is why IDH testing is so important.