This study is the first to report that EGFR amplification, Ch 7+/10−, PDGFRA amplification, CDK4 amplification, and CDKN2A homozygous deletion, which are important for glioma molecular diagnosis, can be analyzed using cfDNA derived from CSF and MLPA if certain conditions regarding the sample cfDNA are met. The gene discussed is CDKN2A; the disease is central nervous system cancer.