Diffuse pediatric-type high grade glioma, RTK1 subtype, subclass C with SYN2 :: PPARG fusion in an older adult

Diffuse pediatric-type high-grade glioma (pHGG), RTK1 subtype, is an uncommon aggressive tumor affecting both children and adults. We describe the case of a 66-year-old woman who presented with a left frontal lobe mass. Following surgical resection, the patient developed herpes simplex virus 2 meningoencephalitis, resulting in death. Histological examination revealed a high-grade glioma demonstrating nuclear pleomorphism, high mitotic activity, vascular proliferation and necrosis. The tumor also exhibited oligodendroglial-like features, nuclear clusters and small true rosette-like structures. Genetic analysis identified partial arm 1p loss and 19q loss, PDGFRA, MYCN and MDM4 amplification, an ATRX mutation and a novel SYN2::PPARG fusion. Homozygous CDKN2A/B deletion was also present. Genomic DNA methylation profiling matched diffuse pediatric-type high-grade glioma, RTK1 subtype, subclass C. This case underscores the importance of utilizing advanced molecular and genomic techniques for accurately diagnosing glial tumors. Further study of the SYN2::PPARG fusion in gliomas could potentially offer insights into its role in glioma biology and possibly help elucidate therapeutic strategies for tumors with PPARG fusions.