Detection of PCNSL- and glioma-specific somatic variants with the TetRS rapid genotyping assay in prospectively collected liquid biopsies. (A) The top row of segmented color bars displays the CNS disease status. The next 4 rows represent the results of routine clinical CSF studies and intraoperative frozen histopathology. The bottom row shows the mutant alleles detected in CSF by the TetRS rapid genotyping assay. Expanded results are shown in supplemental Figure 8. (B) Case P22 shows detection of the MYD88 L265P mutation in CSF from a patient with a cerebellar mass, who underwent gross total resection due to nondiagnostic intraoperative frozen specimen analysis. Cytology and permanent histologic analysis revealed PCNSL 4 days postoperatively. (C) Case P7 shows detection of the TERT C228T mutation in the CSF of a patient with a right temporal mass. Surgical needle biopsy was concluded after intraoperative frozen analysis showed high-grade glioma but converted to open craniotomy and subtotal resection due to intraoperative bleeding. GBM, glioblastoma multiforme; HGG, high-grade glioma.