Neurosurgery notes/Tumours/Gliomas, Glioneuronal Tumors, and Neuronal Tumors/Adult type diffuse astrocytoma/Low grade gliomas/Oligodendroglioma, IDH-mutant and 1p/19q-codeleted

Oligodendroglioma, IDH-mutant and 1p/19q-codeleted

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Parent item
Low grade gliomas
Sub-item
Oligodendroglioma grade 2
Oligodendroglioma grade 3

Definition

  • Essential
    • Diffusely infiltrating, slow growing glioma
    • IDH1 or IDH2 mutation
    • Codeletion of chromosomal arms 1p and 19q
  • Desired
    • Retained nuclear expression of ATRX
      • If loss then it will be astrocytoma
    • TERT promoter mutation

Clinical presentation

  • Seizures
    • 2/3 of all presentations
    • More common in Grade 2 than Grade 3
  • Headache
  • Focal neurologic deficits
  • Mental status change

Origin

  • Unsure if its origin cell is oligodendrocytes

Location

  • Frontal lobe (60%)
  • Temporal and parietal lobes
    • Next most frequent locations
  • Posterior fossa and basal ganglia are uncommon locations for oligodendroglioma
  • Primary spinal cord location is rare, representing 1.5% of oligodendrogliomas
  • In the cortex and white matter of the cerebral hemispheres

WHO Grade

Radiological

CT

  • Hypodense or isodense
  • Well demarcated
  • Majority show Calcifications can be present
    • Grade 2: 25% have calcifications
    • Grade 3 oligodendrogliomas: 50% have calcifications
      • Consistent with their progression from low to higher grade over time (Khalid et al., 2012)
  • Haemorrhage

MRI

  • Heterogenous appearance may indicate areas of haemorrhage or cystic change within the tumour
  • T1
    • Hypointense
  • T2
    • Variably heterogenous hyperintensity with poorly defined margins
    • T2/FLAIR mismatch sign not a feature
  • MRI+C
    • Contrast enhancement = more aggressive
      • Present in < 1/4 of CNS WHO grade 2 tumours
      • Present in > 70% of grade 3 lesions
  • Higher relative cerebral blood volume (rCBV) when compared to IDH-mutant diffuse astrocytoma of a similar grade, thereby mimicking more aggressive disease
  • Lower apparent diffusion coefficient (ADC) values when compared to IDH-mutant diffuse astrocytoma of a similar grade, thereby mimicking more aggressive disease
Images:
  • 48-year-old woman grade
  • WHO 2016
    • Grade II oligodendroglioma, IDHmut.
  • WHO 2021 integrated diagnosis
    • Oligodendroglioma, IDH-mutant, and 1p/19q-codeleted, CNS WHO grade 2
  • The left frontal lobe, incompletely marginated lesion demonstrates
    • Mildly heterogenous high T2w signal (A)
    • Without FLAIR suppression (B)
    • With subtle intrinsic T1-shortening, but without contrast enhancement (C).
A close-up of a brain scan AI-generated content may be incorrect.
  • A 29-year-old man
  • WHO 2016
    • Grade III anaplastic oligodendroglioma, IDHmut.
  • WHO 2021 integrated diagnosis:
    • Oligodendroglioma, IDHmutant and 1p/19q-codeleted, CNS WHO grade 3
  • The right frontoinsular tumour demonstrates
    • Mildly heterogenous high T2w signal (D)
    • Without suppression on FLAIR (E)
    • Partial enhancement, and a small focus of necrosis on post contrast T1w (F)
A close-up of a brain scan AI-generated content may be incorrect.
 
 

Genetic

IDH1, IDH2
Enzymes in Krebs cycle, involved in isocitrate to alphaketoglutarate reaction and NADPH production
1p/19q
Occur as combined deletion of entire chromosome arms 1p/19q after unbalanced translocation between chromosomes 1 and 19 [t(1:19) (q10;p10)]
TERT promoter
Gene located on chromosome 5p15.33 and encodes for the catalytic subunit of telomerase
NOTCH1
Encodes a transmembrane protein that functions in multiple developmental processes and the interactions between adjacent cells

Histopathology

  • Macroscopic
    • Soft, relatively well defined, greyish-pink mass arising in the cortex or subcortical white matter
    • Blurring of the grey-white junction is common
    • Areas of tumour necrosis may be present
    • Calcifications
      • Extreme cases dense calcifications can present as intertumoral stones
    • Cystic degeneration and haemorrhage can be present and rare cases with abundant mucin can appear gelatinous
  • Microscopic
    • Tumour cells are
      • Typically monomorphic
      • Round nuclei
      • Salt and pepper chromatin pattern
      • Inconspicuous nucleoli
    • Histologic features often include a branching capillary pattern and microcalcifications
      • Images
      A close-up of a cell AI-generated content may be incorrect.
      “Fried egg” appearance
      A close-up of a microscope slide AI-generated content may be incorrect.
      Calcifications
      A close-up of a cell AI-generated content may be incorrect.
      “Fried egg” appearance
      A close-up of a pink and black cell AI-generated content may be incorrect.
      Infiltrating cortex
      A microscope view of a cell AI-generated content may be incorrect.
      “Chicken wire” vessels
      A pink and black cells under a microscope AI-generated content may be incorrect.
      Astrocytic histology in an IDH mutant, 1p/19q codeleted tumor
      • Routinely processed formalin fixed, paraffin embedded material often shows artefactual retraction of the cytoplasm due to osmotic damage leading to the characteristic "fried egg/honeycomb" appearance of tumour cells
        • Fried egg/honeycomb is not seen in smear or frozen sections
      • Dense network of fine branching capillaries, classically referred to as a "chicken wire" pattern, is often seen