Diagnostic application of high resolution single nucleotide polymorphism array analysis for children with brain tumors

Single nucleotide polymorphism (SNP) array analysis is currently used as a first tier test for pediatric brain tumors at The Children's Hospital of Philadelphia. The results from 100 consecutive patients are summarized in the present report. Eighty-seven percent of the tumors had at least one pathogenic copy number alteration. Nineteen of 56 low grade gliomas (LGGs) demonstrated a duplication in 7q34, which resulted in a KIAA1549-BRAF fusion. Chromosome band 7q34 deletions, which resulted in a FAM131B-BRAF fusion, were identified in one pilocytic astrocytoma (PA) and one dysembryoplastic neuroepithelial tumor (DNT). One ganglioglioma (GG) demonstrated a 6q23.3q26 deletion that was predicted to result in a MYB-QKI fusion. Gains of chromosomes 5, 6, 7, 11, and 20 were seen in a subset of LGGs. Monosomy 6, deletion of 9q and 10q, and an i(17)(q10) were each detected in the medulloblastomas (MBs). Deletions and regions of loss of heterozygosity that encompassed TP53, RBI, CDKN2A/B, CHEK2, NF1, and NF2 were identified in a variety of tumors, which led to a recommendation for germline testing. A BRAF p.Thr599dup or p.V600E mutation was identified by Sanger sequencing in one and five gliomas, respectively, and a somatic TP53 mutation was identified in a fibrillary astrocytoma. No TP53 hot-spot mutations were detected in the MBs. SNP array analysis of pediatric brain tumors can be combined with pathologic examination and molecular analyses to further refine diagnoses, offer more accurate prognostic assessments, and identify patients who should be referred for cancer risk assessment.