CNS tumor
Embryonal tumors
Medulloblastoma

Author: Nirupama Singh, M.D., Ph.D. (see Authors page)

Revised: 17 February 2017, last major update February 2017

Copyright: (c) 2005-2017, PathologyOutlines.com, Inc.

PubMed search: Medulloblastoma [title]

Related topics: Desmoplastic medulloblastoma

Cite this page: CNS tumor - Medulloblastoma. PathologyOutlines.com website. http://pathologyoutlines.com/topic/cnstumormedulloblastoma.html. Accessed May 25th, 2017.
Definition / general
  • Four genetically defined groups and four histologically defined groups
  • Genetically defined: (a) WNT activated,(b) SHH activated (either TP53 mutated or TP53 wild type), non WNT / non SHH, either (c) medulloblastoma group 3 or (d) medulloblastoma group 4
  • Histologically defined: classic, desmoplastic / nodular, medulloblastoma with extensive nodularity and large cell / anaplastic medulloblastoma
  • Classic is more common in childhood and desmoplastic / nodular in infants and adults
Essential features
  • Small round undifferentiated cells with mild to moderate nuclear pleomorphism
  • High mitotic count
  • Cerebellum and dorsal brain, fourth ventricle
ICD-10 coding
  • C71, C71.6
Epidemiology
  • Medulloblastoma is the most common CNS embryonal tumor of childhood and second only to pilocytic astrocytocytoma of all intracranial neoplasms

  • Classic medulloblastoma:
    • Non WNT / non SHH tumors
    • Midline location
  • Desmoplastic / nodular medulloblastoma:
    • Cerebellar hemispheres and midline
    • Bimodal age distribution
    • Gorlin syndrome: nevoid basal cell carcinoma syndrome
    • SHH activated
    • Favorable outcome in young children compared to nondesmoplastic
  • Medulloblastoma with extensive nodularity:
    • Closely related to desmoplastic medulloblastoma
    • SHH activated
    • Predominantly occurs in infants
    • Excellent outcome
  • Large cell / anaplastic medulloblastoma
    • Undifferentiated cells with marked nuclear pleomorphism, prominent nucleoli, cell wrapping and high mitotic count and apoptotic counts
    • Associated with all genetic variants but more common in SHH activated
Sites
  • Fourth ventricle or cerebellar parenchyma
Clinical features
  • Signs and symptoms of increased intracranial pressure (headache, nausea, vomiting)
Grading
  • WHO grade IV
Radiology description
  • Solid, intensely contrast enhancing masses on CT and MRI
Prognostic factors
  • Medulloblastoma is grade IV tumor with poor prognosis
  • TP53 (p53) mutants have worse prognoses
  • Medulloblastoma with extensive nodularity in infants has good prognosis
  • Desmoplastic / nodular medulloblastoma in young age have relatively good outcome
Case reports
Treatment
  • Surgery, chemotherapy and radiation
  • Efforts have been made to assess an intensified treatment in the context of clinical and biologic risk factors in metastatic medulloblastoma (J Clin Oncol 2016;34:4151)
  • Targeted next generation sequencing of pediatric neuro-oncology patients improves diagnosis, identifies pathogenic germline mutations and directs targeted therapy. (Neuro Oncol 2016 Nov 14 [Epub ahead of print])
Gross images

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Cerebellar tumor extending into fourth ventricle

Microscopic (histologic) description
  • Classic medulloblastoma:
    • Small blue round cell tumor
    • Syncytial arrangement of densely packed undifferentiated cells (embryonal cells)
    • Mitosis with apoptotic bodies
    • Homer Wright rosettes
  • Desmoplastic / nodular medulloblastoma:
    • Densely packed, undifferentiated cells with hyperchromatic and pleomorphic nuclei which produce dense intercellular reticulin fiber network with nodular reticulin free zones
  • Medulloblastoma with extensive nodularity:
    • Expanded lobular architecture as reticulin free nodular zones are enlarged and rich in neuropil-like tissue
  • Large cell / anaplastic medulloblastoma:
    • Anaplasia with marked nuclear pleomorphism, high mitotic count and apoptotic counts
    • Nuclear molding and cell wrapping
  • Medulloblastoma: clinicopathological correlates of SHH, WNT and non SHH / WNT molecular subgroups. (Pathol Res Pract 2016;212:965)
Microscopic (histologic) images

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Large cell / anaplastic

Large cell variant

Sheets of primitive small blue cells

Desmoplastic

Cytology images

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Various images

Positive stains
Negative stains
  • GFAP rarely positive in tumor cells
Molecular / cytogenetics description
Molecular / cytogenetics images

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c-MYC amplification