IDH1 and pilocytic astrocytoma: To validate the sensitivity of the detection system, we included CSF samples of other pediatric brain tumor entities (medulloblastoma n = 5, DMG/pons glioma H3F3A WT n = 3, pilocytic astrocytoma n = 2, HGNET-BCOR n = 1, ependymoma n = 1, LGG n = 1, GBM IDH1 MTn = 1,) and a serum pool of 20 non-tumor bearing pediatric patients.