BRAF duplications and MAPK pathway activation are frequent in gliomas of the optic nerve proper.
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 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.
Department of Pathology, Johns Hopkins Hospital, Baltimore, Maryland 21205, USA. frodrig4@jhmi.edu
Fausto J
FJ
Rodriguez
Azra H
AH
Ligon
Iren
I
Horkayne-Szakaly
Elisabeth J
EJ
Rushing
Keith L
KL
Ligon
Natalie
N
Vena
Denise I
DI
Garcia
J Douglas
JD
Cameron
Charles G
CG
Eberhart
D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000378:metabolism; D005260:Female; D020131:Genes, Duplicate / Q000235:genetics*; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D006801:Humans; D007223:Infant; D020935:MAP Kinase Signaling System / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009456:Neurofibromatosis 1 / Q000473:pathology; D025542:Neurofibromin 1 / Q000378:metabolism; D020339:Optic Nerve Glioma / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology / Q000601:surgery; D051059:PTEN Phosphohydrolase / Q000378:metabolism; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics*; D055815:Young Adult
D019941:Cyclin-Dependent Kinase Inhibitor p16; D005904:Glial Fibrillary Acidic Protein; D025542:Neurofibromin 1; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D020928:Mitogen-Activated Protein Kinases; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human