Beta-catenin Status in Paediatric Medulloblastomas: Correlation of Immunohistochemical Expression With Mutational Status, Genetic Profiles, and Clinical Characteristics

J Pathol. 2009 May;218(1):86-94. doi: 10.1002/path.2514.

Abstract

Medulloblastoma is the most frequent malignant paediatric brain tumour. The activation of the Wnt/beta-catenin pathway occurs in 10-15% of medulloblastomas and has been recently described as a marker for favourable patient outcome. We report a series of 72 paediatric medulloblastomas evaluated for beta-catenin protein expression, CTNNB1 mutations, and comparative genomic hybridization. Gene expression profiles were also available in a subset of 40 cases. Immunostaining of beta-catenin showed extensive nuclear staining (>50% of the tumour cells) in six cases and focal nuclear staining (<10% of cells) in three cases. The other cases either exhibited a signal strictly limited to the cytoplasm (58 cases) or were negative (five cases). CTNNB1 mutations were detected in all beta-catenin extensively nucleopositive cases. The expression profiles of these cases documented strong activation of the Wnt/beta-catenin pathway. Remarkably, five out of these six tumours showed a complete loss of chromosome 6. In contrast, cases with focal nuclear beta-catenin staining, as well as tumours with negative or cytoplasmic staining, never demonstrated CTNNB1 mutation, Wnt/beta-catenin pathway activation or chromosome 6 loss. Patients with extensive nuclear staining were significantly older at diagnosis and were in continuous complete remission after a mean follow-up of 75.7 months (range 27.5-121.2 months) from diagnosis. All three patients with focal nuclear staining of beta-catenin died within 36 months from diagnosis. Altogether, these data confirm and extend previous observations that CTNNB1-mutated tumours represent a distinct molecular subgroup of medulloblastomas with favourable outcome, indicating that therapy de-escalation should be considered. International consensus on the definition criteria of this distinct medulloblastoma subgroup should be achieved.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Child
  • Child, Preschool
  • Comparative Genomic Hybridization
  • DNA Mutational Analysis
  • Female
  • Gene Expression Profiling / methods
  • Humans
  • Immunohistochemistry
  • Infant
  • Male
  • Medulloblastoma / genetics
  • Medulloblastoma / metabolism*
  • Medulloblastoma / mortality
  • Mutation
  • Oligonucleotide Array Sequence Analysis
  • Survival Rate
  • beta Catenin / analysis
  • beta Catenin / genetics
  • beta Catenin / metabolism*

Substances

  • CTNNB1 protein, human
  • beta Catenin