NCCN updated its guidelines to recommend cerebrospinal fluid (CSF)-based molecular tumor profiling for high-grade glioma and glioblastoma when tissue biopsy is not feasible. The recommendation positions CSF sampling as an adjunctive diagnostic route via lumbar puncture, including when treatment depends on molecular markers. The guideline update specifically broadens the list of CNS cancers where CSF testing is recommended and adds inoperable HGG and GBM. Belay Diagnostics said the change supports its CSF-based assays, including the Summit 2.0 genomic profiling panel, the Ascent chromosomal instability assay, and the Vantage MGMT promoter methylation assay. Belay previously published analytical and clinical validation work for Summit 2.0 earlier this year and highlighted that each assay can be performed using a single CSF specimen. NCCN’s decision underscores growing acceptance of liquid biopsy-style diagnostics beyond oncology settings where tissue sampling is straightforward. For clinical laboratories and neuro-oncology programs, the shift can shorten time-to-molecular results and help expand testing access for patients who cannot undergo neurosurgical biopsy.