CNS & pituitary tumors
Embryonal tumors
Medulloblastoma
Medulloblastoma
Author: Nirupama Singh, M.D., Ph.D.
Last author update: 1 February 2017
Last staff update: 13 April 2022 (update in progress)
Copyright: 2005-2023, PathologyOutlines.com, Inc.
PubMed search: Medulloblastoma [title] (Review[ptyp] AND "loattrfree full text"[sb])
Related topics: Desmoplastic medulloblastoma
Table of Contents
Definition / general | Essential features | ICD coding | Epidemiology | Sites | Clinical features | Grading | Radiology description | Prognostic factors | Case reports | Treatment | Gross images | Microscopic (histologic) description | Cytology images | Positive stains | Negative stains | Molecular / cytogenetics descriptionCite this page: Singh N. Medulloblastoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/cnstumormedulloblastoma.html. Accessed June 4th, 2023.
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
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)
- Large cell / anaplastic (pending)
- Non WNT / non SHH (pending)
- With extensive nodularity (pending)
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
- 2 year old boy with WNT activated medulloblastoma with melanotic and myogenic differentiation (Neuropathology 2016;36:372)
- Young child with PTCH1 mutation in addition to Gorlin syndrome and medulloblastoma (Pediatr Blood Cancer 2016;63:1128)
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
Images hosted on other servers:
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)
Cytology images
Images hosted on other servers:
Various images
Positive stains
- Synaptophysin, NeuN
- Nuclear SMARCB1 / INI1 and SMARCA4 are retained
- Medulloblastoma with melanocytic differentiation: HMB45, melanA
- Medulloblatoma with myogenic differentiation: desmin and myogenin
- Expression of SOX11, PAX5, TTF1 and ISL1 in medulloblastoma (Pathol Res Pract 2016;212:965)
Negative stains
- GFAP rarely positive in tumor cells
Molecular / cytogenetics description
- GAB1 and YAP1 immunopositivity indicate SHH activated tumors and immunonegativity suggests non WNT / non SHH tumors (Neuropathol Appl Neurobiol 2015;41:135)
