Supplementary figures 1-4 and supplementary table 3. Supplementary figure 1. Genomic DNA validation of probes, assessing sensitivity, and specificity of ddPCR platform. Supplementary figure 2. Novel detection of histone 3 mutation in fluid present in a brainstem tumor cyst found in a DIPG patient at postmortem. Supplementary figure 3. Longitudinal changes in plasma ctDNA in association with MR imaging findings and clinical assessments. Supplementary figure 4. Biofluid ctDNA and tumor spread as assessed by MRI, genomic, and/or histological studies. Supplementary table 3. Mutations analyzed in the study by ddPCR with corresponding design of primers and probes.