Utility of Comprehensive Genomic Profiling for Precise Diagnosis of Pediatric-Type Diffuse High-Grade Glioma.

In the current World Health Organization classification of central nervous system tumors, comprehensive genetic and epigenetic analyses are considered essential for precise diagnosis. A 14-year-old male patient who presented with a cerebellar tumor was initially diagnosed with glioblastoma and treated with radiation and concomitant temozolomide chemotherapy after resection. During maintenance temozolomide therapy, a new contrast-enhanced lesion developed in the bottom of the cavity formed by the resection. A second surgery was performed, but the histological findings in specimens from the second surgery were different from those of the first surgery. Although genome-wide DNA methylation profiling was conducted using frozen tissue for a precise diagnosis, the proportion of tumor cells was insufficient and only normal cerebellum was observed. We then performed comprehensive genetic analysis using formalin-fixed paraffin-embedded sections, which revealed MYCN amplification without alteration of IDH1, IDH2, or Histone H3. Finally, the patient was diagnosed with pediatric-type diffuse high-grade glioma, H3-wildtype and IDH-wildtype. In conclusion, comprehensive genetic and epigenetic analysis should be considered in pediatric brain tumor cases.