Nervous system: Medulloblastoma

2000-07-01   Anne Marie Capodano 

1.Laboratoire de Cytogénétique Oncologique, Hpital de la Timone, 264 rue Saint Pierre, 13005 Marseille, France

Clinics and Pathology

Epidemiology

It represents 10 at 20 % of brain tumours and 30 % of tumours localized in posterior fossa; annual incidence is 0,5 per 100 000 children; peak of occurrence at 7 years.
Atlas Image
Histological features of a typical medulloblastoma: Homer-Wright rosettes - Anne Marie Capodano.

Pathology

Belongs to the primitive neurectodermal tumours (PNET): highly malignant embryonal tumours of the CNS with predominant neuronal differentiation.
Several variants medulloblastoma are recognized in the OMS classification :
  • Classic medulloblastoma composed of densely jacked round-cells with round to oval hyperchromatic nuclei.
  • Desmoplastic medulloblastoma represents a variant with abundant reticulin and collagen.
  • Large cell medulloblastoma is a rare variant composed of cells with large round nuclei.
    Immuno histo chemistry : Classic medulloblastoma is strongly immuno-reactive for Vimentin. Some tumours are immunoreactive for NSE, Synaptophysine and GSAP.
  • Treatment

    The treatment associates total surgical resection and radiotherapy or, according to the age, chemotherapy.

    Prognosis

    Survival without recurrence is 50 at 70 %; depends on the quality of surgical resection and on the presence of metastases at the time of diagnosis.

    Cytogenetics

    Atlas Image
    i(17q) - R-banding.

    Cytogenetics morphological

  • The most common specific abnormality in medulloblastomas, which is present in approximately 50 % of cases, is isochromosome 17q [i(17q)]. The breakpoint is in the proximal portion of p-arm at 17p11.2, so that the resultant structure is dicentric. In a few cases, partial or complete loss of 17p occurs through interstitial deletion, unbalanced translocation or monosomy 17.
  • Chromosome 1 is also involved in medulloblastomas. The most frequent abnormalities are unbalanced translocations, deletions and duplications. Rearrangements of chromosome 1 often result in trisomy 1q without loss of the p-arm.
  • Others less common chromosomal changes are: deletions of 6q, 9q, 10q, 11q, 11p and 16q, monosomy 22 and in rare cases double minutes.
  • Cytogenetics molecular

  • Isochromosome 17 q has been observed in interphase nuclei using fluorescence in situ hybridization. This technique is used in particular when only a few metaphases are obtained or when only normal diploid cells are obtained in culture.
  • Genes Involved and Proteins

    Note

  • Studies on loss of heterozygosity (LOH) have confirmed loss of portions of 17p in 30-45 % of cases. Some studies showed a correlation between LOH for 17p and a poor response to therapy and shortened survival. Mutations of p53 gene located on 17p13 have been found in only 5-10 % of these tumors.
  • Expression of PAX5 and PAX6 mRNA was shown in 70 % of medulloblastomas. The precise mechanism by which these genes are involved remains unknown.
  • Inactivation of PTCH tumor suppressor gene occurs in a subset of medulloblastomas.
  • Bibliography

    Pubmed IDLast YearTitleAuthors
    24871541989Isochromosome 17q in primitive neuroectodermal tumors of the central nervous system.Biegel JA et al
    34220501988Structural chromosomal abnormalities in human medulloblastoma.Bigner SH et al
    16696881990Cytogenetics and molecular genetics of malignant gliomas and medulloblastoma.Bigner SH et al
    36045791987Differentiation in the medulloblastoma. A histological and immunohistochemical study.Burger PC et al
    19790501990Deletion mapping of the medulloblastoma locus on chromosome 17p.Cogen PH et al
    19009661991"Desmoplastic" versus "classic" medulloblastoma: comparison of DNA content, histopathology and differentiation.Giangaspero F et al
    106194951999Molecular genetic studies of chromosome 11 and chromosome 22q DNA sequences in pediatric medulloblastomas.Lescop S et al
    100643951999Diagnostic markers in paediatric medulloblastoma: a Paediatric Oncology Group Study.McLendon RE et al
    13940991992Detection of an i(17q) chromosome by fluorescent in situ hybridization with a chromosome 17 alpha satellite DNA probe.Nakagawa H et al
    93072911997Extensive genomic abnormalities in childhood medulloblastoma by comparative genomic hybridization.Reardon DA et al
    79877941994Detection of i(17q) chromosome by fluorescent in situ hybridization (FISH) with interphase nuclei in medulloblastoma.Vagner-Capodano AM et al
    25393241989Detection of 1q polysomy in interphase nuclei of human solid tumors with a biotinylated probe.Viegas-Péquignot E et al

    External Links

    Citation

    Anne Marie Capodano

    Nervous system: Medulloblastoma

    Atlas Genet Cytogenet Oncol Haematol. 2000-07-01

    Online version: http://atlasgeneticsoncology.org/solid-tumor/5065/medulloblastomaid5065