Copy number alterations determined by single nucleotide polymorphism array testing in the clinical laboratory are indicative of gene fusions in pediatric cancer patients.

Gene fusions resulting from structural rearrangements are an established mechanism of tumorigenesis in pediatric cancer. In this clinical cohort, 1,350 single nucleotide polymorphism (SNP)-based chromosomal microarrays from 1,211 pediatric cancer patients were evaluated for copy number alterations (CNAs) associated with gene fusions. Karyotype or fluorescence in situ hybridization studies were performed in 42% of the patients. Ten percent of the bone marrow or solid tumor specimens had SNP array-associated CNAs suggestive of a gene fusion. Alterations involving ETV6, ABL1-NUP214, EBF1-PDGFRB, KMT2A(MLL), LMO2-RAG, MYH11-CBFB, NSD1-NUP98, PBX1, STIL-TAL1, ZNF384-TCF3, P2RY8-CRLF2, and RUNX1T1-RUNX1 fusions were detected in the bone marrow samples. The most common alteration among the low-grade gliomas was a 7q34 tandem duplication resulting in a KIAA1549-BRAF fusion. Additional fusions identified in the pediatric brain tumors included FAM131B-BRAF and RAF1-QKI. COL1A1-PDGFB, CRTC1-MAML2, EWSR1, HEY1, PAX3- and PAX7-FOXO1, and PLAG1 fusions were determined in a variety of solid tumors and a novel potential gene fusion, FGFR1-USP6, was detected in an aneurysmal bone cyst. The identification of these gene fusions was instrumental in tumor diagnosis. In contrast to hematologic and solid tumors in adults that are predominantly driven by mutations, the majority of hematologic and solid tumors in children are characterized by CNAs and gene fusions. Chromosomal microarray analysis is therefore a robust platform to identify diagnostic and prognostic markers in the clinical setting.