title: BRAF-V600E immunohistochemistry in a large series of glial and glial-neuronal tumors.
abstract: Some glial-neuronal tumors (GNT) (pleomorphic xantho-astrocytoma [PXA], ganglioglioma [GG]) display BRAF-V600E mutation, which represents a diagnostic clue to these entities. Targeted therapies against BRAF-V600 protein have shown promising results in GNT. The aim of this study was to assess the utility of BRAF-V600E immunohistochemistry (IHC, clone VE1) in daily practice in a series of 140 glial, and GNT compared to molecular biology (MB) techniques.
  
  
  
  We performed BRAF-V600E IHC on all 140 cases. We used Sanger sequencing and allele-specific quantitative PCR (ASQ-PCR) to detect BRAF-V600E mutation when sufficient amount of materiel was available.
  
  
  
  BRAF-V600E immunostaining was detected in 29.5% of cases (41/140 cases; 61.5% GG/GC/AGG (32/52), 33% PXA, 6.6% pilocytic astrocytomas). In 47 cases, MB could be performed: Sanger sequencing and ASQ-PCR in 34 cases, ASQ-PCR only in 11 cases, and Sanger sequencing only in two cases. In initial tumors, Sanger sequencing identified BRAF-V600E mutation in 19.5% tumors (seven of 36 tested cases). ASQ-PCR showed mutation in 48.5% tumors (17/35 tested cases). In six cases (5 GG, one PXA), the results were discordant between IHC and MB; the five GG cases were immunopositive for BRAF-V600E but wild type with both MB techniques. In another 7 GG, the percentage of mutated (ganglion) cells was low, and Sanger sequencing failed to detect the mutation, which was detected by IHC and ASQ-PCR.
  
  
  
  In tumors with few mutated cells (e.g., GG), anti-BRAF-V600E IHC appears more sensitive than Sanger sequencing. The latter, although considered as the gold standard, is not to be used up-front to detect BRAF mutation in GG. The combination of IHC and ASQ-PCR appears more efficient to appraise the indication of targeted therapies in these glioneuronal tumors.
authors.affiliation: Pathology Department Angers University Hospital Angers France.
authors.forename: Quentin
authors.identifier: 0000-0002-6327-678X
authors.initials: Q
authors.lastname: Breton
authors.affiliation: Pathology Department Angers University Hospital Angers France.
authors.forename: Hélène
authors.initials: H
authors.lastname: Plouhinec
authors.affiliation: Genetics and Biochemistry Department Angers University Hospital Angers France.
authors.forename: Delphine
authors.initials: D
authors.lastname: Prunier-Mirebeau
authors.affiliation: Pathology Department Angers University Hospital Angers France; INSERM UMR-1066, Micro- and Nanomedicine Biomimetics (MINT) Angers University Hospital Angers France.
authors.forename: Blandine
authors.initials: B
authors.lastname: Boisselier
authors.affiliation: Pathology Department Angers University Hospital Angers France.
authors.forename: Sophie
authors.initials: S
authors.lastname: Michalak
authors.affiliation: INSERM UMR-1066, Micro- and Nanomedicine Biomimetics (MINT) Angers University Hospital Angers France; Neurosurgery Department Angers University Hospital Angers France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Menei
authors.affiliation: Pathology Department Angers University Hospital Angers France; INSERM UMR-1066, Micro- and Nanomedicine Biomimetics (MINT) Angers University Hospital Angers France.
authors.forename: Audrey
authors.initials: A
authors.lastname: Rousseau
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D016543:Central Nervous System Neoplasms / Q000175:diagnosis* / Q000235:genetics; D002648:Child; D002675:Child, Preschool; D005260:Female; D005910:Glioma / Q000175:diagnosis* / Q000235:genetics; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods / Q000592:standards*; D007223:Infant; D008297:Male; D008875:Middle Aged; D009154:Mutation; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics*; D060888:Real-Time Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D017422:Sequence Analysis, DNA / Q000379:methods / Q000592:standards*; D055815:Young Adult
chemical_list: C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf
keywords: BRAF‐V600E mutation; E19294; RRID: AB_11203852; Sanger sequencing; Spring Bioscience VE1; allele‐specific quantitative PCR; ganglioglioma; glial–neuronal tumor; immunohistochemistry