High-grade glioma PD-L1 expression has been identified in 6 (30%) of 20 pediatric high-grade glioma samples, 42 and larger studies in adults showed expression in 68% of 62 glioblastoma samples, with a strong trend for worse outcome in these patients. 43 In addition, a subset of pediatric high-grade glioma tumors has evidence of MSI, which reflects the increased mutational status of the tumor and the potential greater number of neoantigens that could induce a host immune response.
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