Fig. 1.

Agarose gel electrophoresis shows discrete bands at 150 and 300 bp exclusively in lanes of cell-free DNA extracted from cerebrospinal fluid of two patients (left) compared with widespread smear bands for corresponding tumor-tissue DNA (right). Two representative samples show that a high concentration of cell-free (cf)DNA can be extracted from intracranial cerebrospinal fluid. Since the concentration of cfDNA was low, we did not adjust the concentration. a Recurrent anaplastic oligodendroglioma in a 43-year-old female; cfDNA concentration, 4.3 ng/μL. b First onset of diffuse midline glioma with H3 K27M in a 46-year-old female; DNA concentration, 4.1 ng/μL. Tumor DNA 15.0 ng/μL was loaded