Pleomorphic xanthoastrocytoma (PXA) is an uncommon low-grade glial neoplasm of the central nervous system that most frequently affects children and young adults 
. The tumors often arise in the temporal lobe and involve both the superficial cortex and the overlying meninges 
. During the clinical evaluation of PXA resection specimens, the dense cellularity and pleomorphism typical of PXA raises a differential diagnosis including ganglioglioma and a range of high-grade malignancies like glioblastoma (GBM), giant cell glioblastoma (gcGBM), gliosarcoma or pleomorphic sarcoma 
. The presence of eosinophilic granular bodies and the compact, predominantly non-infiltrating nature of PXA also can introduce pilocytic astrocytoma into the differential diagnosis 
. The histopathologic diagnosis of PXA can often be accomplished readily when the histologic findings are carefully considered in light of the clinical and radiological features, although the diagnosis can be challenging and confusion with other neoplasms can occur 
. A reproducible ancillary diagnostic marker for PXA would, therefore, be of significant clinical use.
PXA are typically slow growing at presentation and as a result patients commonly experience long-standing seizures. While the prognosis is relatively favorable, the recurrence rate following resection is 30% within five years and about 40% within ten years. The overall survival rate is 80% at five years and 70% at ten years 
. In its classic form, the histology of the tumors is distinct with large pleomorphic giant cells demonstrating xanthomatous change, a dense deposition of intercellular reticulin and the presence of eosinophilic granular bodies 
. Anaplastic changes such as high mitotic activity and necrosis are uncommon at initial presentation but become increasingly frequent in recurrences 
. The treatment of PXA typically involves surgical resection followed by radiological monitoring 
. Recurrent lesions or tumors that demonstrate anaplastic features at primary resection are treated with radiation 
and chemotherapeutic protocols 
that are also used for anaplastic astrocytoma and glioblastoma. The development of more selective targeted therapies for PXA and the design of future clinical trials are dependent on an understanding of the molecular genetic lesions that drive its pathogenesis.
Identification of genetic lesions in PXA has been challenging for a number of reasons. Most notably, the number of patients with PXA is low even in large academic hospital centers resulting in a paucity of cases for investigation. Since few tumor banks have frozen PXA samples most analyses must be done on formalin-fixed paraffin-embedded (PXA) tissue and robust technologies for analyzing DNA from FFPE sources have only recently emerged 
. In addition, PXA cell lines are not available and animal models have not been generated. To date, molecular genetic analysis of PXA has been predominantly limited to TP53
revealing mutations in 6% of cases (7 of 123) 
. There is no correlation between mutated TP53
and the presence of anaplastic features. While amplifications of the EGFR
loci are absent 
, array CGH analysis demonstrated homozygous loss of the 9p21.3 locus containing CDKN2A/CDKN2B
in 6 of 10 cases 
Recently, multiplexed targeted sequencing platforms have been developed that can be used to simultaneously investigate the mutation status of multiple key cancer genes 
. These assays are capable of robustly identifying mutations in DNA derived from FFPE samples and allow for the rapid identification of clinically important and therapeutically tractable genetic mutations. In this study, we use the SNaPshot mutation profiling assay to investigate the mutation status of 15 cancer associated genes in 26 PXA and 71 GBM.