Molecular Analysis of Pediatric Oligodendrogliomas Highlights Genetic Differences with Adult Counterparts and Other Pediatric Gliomas

摘要

Oligodendroglioma represents a distinctive neoplasm in adults but similar neoplasms occur rarely in children. We studied 20 cases of pediatric oligodendroglioma by SNP array (median age 9 years, range 1-19; 15 grade II and 5 grade III). Cytogenetic abnormalities were present in 8 (53%) grade II and all five anaplastic oligodendrogliomas. Most changes were in the form of deletion and copy neutral loss of heterozygosity (LOH). The most common abnormality was 1p deletion (n=5). Whole arm 1p19q co-deletion was present in three cases from adolescent patients and 9p loss in 3, including one low-grade oligodendroglioma with CDKN2A homozygous deletion. Common losses were largely limited to the anaplastic subset (n=5) and included 3q29 (n=3), 11p (n=3), 17q (n=3), 4q (n=2), 6p (n=2), 13q (n=2), 14q (n=2), 17p (n=2) and whole Ch 18 loss (n=2). Gains were non-recurrent except for whole Ch 7 (n=2) and gain on 12q (n=2) including the MDM2 locus. Possible germ line LOH (or uniparental disomy) was present in seven cases (35%), with one focal abnormality (22q13.1-13.2) in two. BRAF-KIAA1549 fusions and BRAF p.V600E mutations were absent (n=13 and 8). In summary, cytogenetic alterations in pediatric oligodendrogliomas are characterized mostly by genomic losses, particularly in anaplastic tumors.