title: Molecular stratification of medulloblastoma: comparison of histological and genetic methods to detect Wnt activated tumours.
abstract: OBJECTIVE
  Wnt activation in medulloblastomas is associated with good outcome. Upfront testing and risk-adapted stratification of patients will be done in future clinical studies. In a cohort of 186 paediatric medulloblastomas our aim was to identify the optimal methods in standard clinical practice to detect this subgroup.
  
  
  METHODS
  Nuclear accumulation of β-catenin was analysed by immunohistochemistry (IHC). DNA of FFPE tissue was amplified by PCR for single-strand conformation polymorphism analysis and direct sequencing of CTNNB1 exon 3. Copy number of chromosome 6 was analysed by multiplex ligation-dependent probe amplification and molecular inversion profiling.
  
  
  RESULTS
  Different automated immunostaining systems showed similar results. Twenty-one of 186 samples had nuclear accumulation in ≥5% of cells, 17 samples showed <5% β-catenin positive nuclei. None of these 17 cases had CTNNB1 mutations, but 18 of 21 cases with ≥5% accumulation did, identifying these 18 cases as Wnt-subgroup medulloblastomas. Fifteen of 18 mutated cases showed monosomy 6, 3 had balanced chromosome 6. On the contrary, none of the CTNNB1 wild-type tumours had monosomy 6.
  
  
  CONCLUSIONS
  Standard neuropathological evaluation of medulloblastoma samples should include IHC of β-catenin because tumours with high nuclear accumulation of β-catenin most probably belong to the Wnt subgroup of medulloblastomas. Still, IHC alone may be insufficient to detect all Wnt cases. Similarly, chromosome 6 aberrations were not present in all CTNNB1-mutated cases. Therefore, we conclude that sequencing analysis of CTNNB1 exon 3 in combination with β-catenin IHC (possibly as pre-screening method) is a feasible and cost-efficient way for the determination of Wnt medulloblastomas.
authors.affiliation: Department of Neuropathology, University of Bonn Medical Centre, Bonn, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Goschzik
authors.forename: Anja
authors.initials: A
authors.lastname: Zur Mühlen
authors.forename: Glen
authors.initials: G
authors.lastname: Kristiansen
authors.forename: Christine
authors.initials: C
authors.lastname: Haberler
authors.forename: Harald
authors.initials: H
authors.lastname: Stefanits
authors.forename: Carsten
authors.initials: C
authors.lastname: Friedrich
authors.forename: Katja
authors.initials: K
authors.lastname: von Hoff
authors.forename: Stefan
authors.initials: S
authors.lastname: Rutkowski
authors.forename: Stefan M
authors.initials: SM
authors.lastname: Pfister
authors.forename: Torsten
authors.initials: T
authors.lastname: Pietsch
mesh_terms: D000293:Adolescent; D002528:Cerebellar Neoplasms / Q000235:genetics*; D002648:Child; D002675:Child, Preschool; D002896:Chromosomes, Human, Pair 6 / Q000235:genetics*; D004252:DNA Mutational Analysis / Q000379:methods*; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008527:Medulloblastoma / Q000235:genetics*; D060885:Multiplex Polymerase Chain Reaction; D018807:Polymorphism, Single-Stranded Conformational; D060449:Wnt Signaling Pathway / Q000502:physiology*; D055815:Young Adult; D051176:beta Catenin / Q000235:genetics*
chemical_list: C495270:CTNNB1 protein, human; D051176:beta Catenin
keywords: Wnt signalling; immunohistochemistry; medulloblastoma; mutation analysis; sequencing; β-catenin