Pre-operative CSF diversion, often performed to relieve obstructive hydrocephalus and assess GCT markers (β-hCG, AFP), provides a unique opportunity to integrate cfDNA sequencing into diagnostics, with CNVs as a potential biomarker due to the high frequency of CNVs reported in pineoblastoma and CNS GCTs [62, 63], and their high specificity for malignancy. The gene discussed is AFP; the disease is pineoblastoma.