BRAF duplications and MAPK pathway activation are frequent in gliomas of the optic nerve proper

Fausto J. Rodriguez, Azra H. Ligon, Iren Horkayne-Szakaly, Elisabeth J. Rushing, Keith L. Ligon, Natalie Vena, Denise I. Garcia, J. Douglas Cameron, Charles G. Eberhart

Research output: Contribution to journalArticle

Abstract

Optic pathway gliomas represent a specific subtype of astrocytoma with unique clinicopathologic and biologic properties, but studies of tumors in the optic nerve proper have been hampered by limited tissue availability. We analyzed optic nerve gliomas of 59 patients (median age, 9 years; range, 3 months-66 years; 33 female, 26 male) using formalin-fixed paraffin-embedded material in tissue microarrays. Seven patients had the clinical diagnosis of neurofibromatosis type 1 (NF1). Fluorescence in situ hybridization studies were performed for BRAF, PTEN, CDKN2A (p16), and NF1. Immunohistochemistry was performed for glial fibrillary acidic protein, phospho-ERK, and mutant IDH1 R132H protein. The BRAF duplication was present in 11 (73%) of 15 evaluable tumors, including 1 NF1 patient (1 of 4 tested; 25%). The single tumor lacking BRAF duplication or NF1 association had histologic features of a ganglioglioma. Conversely, heterozygous PTEN deletions were present in 2 (8%) of 25 evaluable cases, one of which was BRAF duplicated and the other was NF1 associated. CDKN2A and NF1 deletions were absent in all tumors tested. Phospho-ERK immunoreactivity was present in 55 (96%) of 57 tumors and was mostly strong and diffuse (80%). Only 1 case of 53 expressed IDH1. Thus, optic nerve gliomas demonstrated molecular alterations typical of pilocytic astrocytomas, including the universal presence of either BRAF duplication or NF1 association and common mitogen-activated protein kinase pathway activation but very rare mutant IDH1 expression.

Original languageEnglish (US)
Pages (from-to)789-794
Number of pages6
JournalJournal of neuropathology and experimental neurology
Volume71
Issue number9
DOIs
StatePublished - Sep 1 2012

Keywords

  • BRAF
  • Fluorescence in situ hybridization
  • Glioma
  • MAPK
  • Neurofibromatosis
  • Optic nerve
  • Pilocytic astrocytoma

ASJC Scopus subject areas

  • Pathology and Forensic Medicine
  • Neurology
  • Clinical Neurology
  • Cellular and Molecular Neuroscience

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