Neurosurgery notes/Tumours/Gliomas, Glioneuronal Tumors, and Neuronal Tumors/Glioneuronal and neuronal tumours/Myxoid glioneuronal tumor

Myxoid glioneuronal tumor

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Glioneuronal and neuronal tumours

Definition

  • Essential:
    • Oligodendrocyte-like tumour cells embedded in a prominent myxoid stroma AND
    • Location in septal nuclei, septum pellucidum, corpus callosum, or periventricular white matter
  • Desirable:
    • PDGFRA p.K385L/l dinucleotide mutation or (less commonly) other mutations in the extracellular domain of PDGFRA
    • Methylation profile of myxoid glioneuronal tumour

Numbers

  • Wide age range in children and adults
  • 2% of all CNS tumours

Localisation

  • Septum pellucidum (4/8)
    • Stereotypical
  • Genu/rostrum of the corpus callosum (3/8)
  • Immediate periventricular white matter

Genetic mutation

  • A recurrent dinucleotide mutation in the PDGFRA gene
    • Encodes platelet-derived growth factor receptor alpha (PDGFRA)
      • A transmembrane receptor tyrosine kinase.
    • Mutation results in substitution of lysine with either leucine or isoleucine at codon 385 (p.K385L or p.K385l)
    • Causes constitutive activation of the intracellular tyrosine kinase domain (TKD) and downstream activation of the PI3K and МАРК signalling pathways

Grading

  • CNS WHO grade 1

Pathology

  • Oligodendrocyte-like cells in a myxoid stroma reminiscent of DNET
  • Low cellularity proliferation of oligodendrocyte-like cells with monotonous round to oval nuclei, small nucleoli, and scant to moderate eosinophilic cytoplasm within a mucin-rich stroma
 
Myxoid glioneuronal tumor is a tumor typically arising in the septal region and involving the lateral ventricle. It is characterized by a proliferation of oligodendrocyte-like tumor cells embedded in a prominent myxoid stroma, often including admixed floating neurons, neurocytic rosettes, and/or perivascular neuropil, and by a dinucleotide mutation in the PDGFRA gene. (A) Common septal location (magnetic resonance imaging, T1 with contrast) and (B) characteristic histological features with small round cells and myxoid stroma (H&E, ×200).
Myxoid glioneuronal tumor is a tumor typically arising in the septal region and involving the lateral ventricle. It is characterized by a proliferation of oligodendrocyte-like tumor cells embedded in a prominent myxoid stroma, often including admixed floating neurons, neurocytic rosettes, and/or perivascular neuropil, and by a dinucleotide mutation in the PDGFRA gene. (A) Common septal location (magnetic resonance imaging, T1 with contrast) and (B) characteristic histological features with small round cells and myxoid stroma (H&E, ×200).

Clinical features

  • Headache
    • Most common
  • Seizures
  • Behavioural changes
  • Visual symptoms
  • HCP
    • Tumours centred in the septal nuclei and septum pellucidum can be associated with obstructive hydrocephalus
  • A subset of patients have presented with intraventricular disseminated disease at the time of presentation

Radiology

CT

  • Hypodensity

MRI

  • T2w hyperintense
  • Lacking contrast enhancement
  • Diffusion restriction
  • FLAIR
    • Has been highlighted as diagnostic if it shows partially suppressed signal at the centre of the lesion resembling a T2-FLAIR mismatch as previously described in septal DNETs
notion image

Prognosis

  • The majority were cured through surgical excision with only a minority needing further treatment

Reference