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HomeTumors of the Nervous System in ChildrenInfratentorial Tumors In Children HomepageMedulloblastomas in Children HomepagePathology of Medulloblastomas in Children

Pathology of Medulloblastomas in Children

This page was last updated on May 9th, 2017

Molecular/Genetic Pathology

  • Molecular variants with prognostic significance: Recent genomic studies have determined that medulloblastomas have distinct molecular variants based on immunohistochemical markers: DKK1 (WNT), SFRP1 (SHH), NPR3, and KCNA1.  These variants have important prognostic implications, as the progression-free and overall survival rates are dramatically different among subgroups (27).

Histopathology

  • W.H.O. Grade IV: Medulloblastomas are malignant tumors that are categorized as W.H.O. Grade IV (12).
  • Densely packed cells on low-power magnification: Medulloblastomas are composed of densely packed cells with hyperchromatic nuclei and scant cytoplasm (12).

Medulloblastoma on low-power magnification: The histopathology shows typical sheets of undifferentiated cells

 

  • Nuclear pleomorphism with rosettes on high power: Tumors have significant nuclear pleomorphism, high mitotic activity, and neuroblastic (Homer Wright) rosettes in fewer than 40% of cases.

Medulloblastoma on higher power magnification: This view of a medulloblastoma shows an area with neuroblastic (Homer Wright) rosettes

 

  • Immunohistochemistry: Medulloblastomas most commonly have neuronal differentiation, which is manifested by immunopositivity for neuronal markers such as synaptophysin.

Medulloblastoma stained for synaptophysin: Synaptophysin positivity in medulloblastoma shows as a brown staining of the cells

 

  • MIB-1 labeling index: The MIB-1 level is typically very high, reflecting significant cellular proliferation.

MIB-1 labeling stain of medulloblastoma: A high MIB-1 labeling index is apparent

 

  • Histologic variants: Histological subtypes have been described that have varying responses to treatments. They include desmoplastic/nodular medulloblastoma, medulloblastoma with extensive nodularity, anaplastic medulloblastoma, large cell medulloblastoma, myogenic differentiation (medullomyoblastoma), and melanocytic differentiation (melanocytic medulloblastoma) (12).
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Epidemiology of Medulloblastomas in Children
Presentation of Medulloblastomas in Children

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