Tag: astrocytoma

Grading classifies different histological types and also within each type. Arabic numerals (1, 2, 3, 4) are used instead of Roman numbers.

Eg: Astrocytoma, IDH Mutant, CNS WHO Grade 2

Total 4 grades only.

Grade 1

Circumscribed tumours.

  • Pilocytic astrocytoma (Well circumscribed)
  • Diffuse astrocytoma MYB altered
  • Angiocentric glioma
  • PLNTY
  • Multinodal & vacuolating neuronal tumour
  • Subependymoma
  • Myxopapillary ependymoma
  • Meningioma (most of them except 4 below)
  • SFT (can be 1, 2, 3)
  • Chordoma
  • Ganglioglioma

Grade 2, 3 (3 = anaplastic)

2 = infiltrating.
3 = evidence of malignancy. eg: Anaplastic ependymoma/astrocytoma/oligodendroglioma

  • Astrocytoma, IDH Mutant
  • Oligodendroglioma, IDH Mutant
  • Pleomorphic xanthoastrocytoma
  • Chordoid glioma (all mixed gliomas)
  • Ependymoma
  • Supratentorial, Posterior fossa Ependymoma
  • G2 meningiomas: Clear cell, Chordoid, Atypical Meningiomas
  • G3 meningiomas: Rhabdoid, Papillary and anaplastic meningioma
  • Central neurocytoma
  • Hemangiopericytoma

Grade 4

Malignant, aggressive, rapid growth and necrosis.

  • Glioblastoma, Gliosarcoma
  • Diffuse midline and diffuse hemispheric glioma
  • All “-blastomas”.
    • Medullo, Pinealo, Ependymo-
  • Atypical teratoid / rhabdoid tumour

WHO grade 2 or 3 astrocytoma with pleomorphic cells.

BRAF V600E Mutation & CDKN2A/2B deletion. Typically IDH Wildtype

Pleomorphic [Multinucleated giant cells + Spindle cells + Lipidized cells] -> transforms to Monomorphic [Rhabdoid / epithelioid] areas

Granular eosinophilic bodies and Pericellular reticulin.

WHO grade 2 if mitosis <2.5/mm2. Grade 3 if >/= 2.5/mm2.

Typical mutations

IDH mutation, ATRX loss, TP53 mutation, CDKN2A/B homozygous deletion, 1p-19q codeletion, H3K27 & H3.3G34R mutation, TERT mutation, EGFR amplification.

Chart

IDH Mutant

  • Astrocytomas (Diffuse) – Typically IDH mutant.
    • IDH mutant ATRX loss / TP53 mutant
    • IDH mutant ATRX and TP53 intact
    • Astrocytoma WHO grade 4 =
      • CDKN2A/B homozygous deletion or
      • Microvascular proliferation, necrosis in CDKN2A/B wildtype (Otherwise grade 2 or 3)
  • Oligodendrogliomas – Typically IDH mutant + 1p/19q codeleted.
    • WHO grade 2 or 3

IDH Wildtype (all are WHO grade 4)

  • Diffuse midline gliomas – IDHwild with H3K27 mutant.
  • Diffuse hemispheric glioma IDHwild with H3.3G34 mutant.
  • Glioblastoma – IDH, H3 Wildtype (Only adult glioma in IDH wildtype family)

Reference

WHO Grade 1 astrocytoma (non-infiltrative or Localised).

Children and young adults.

Discrete borders. Well circumscribed. Benign. Cystic with Mural nodule +.

Site: Third ventricle, optic nerve, spinal core and cerebrum.

MAP kinase pathway alterations. Eg: KIAA1549-BRAF fusion.

No IDH mutation in WHO grade I astrocytoma (only for grade II and III).

Microscopy

  • Bipolar cells with hair like process
  • Fibrillary / Microcystic stroma
  • Rosenthal fibres – Eosinophilic corkscrew structures.
  • Mulbery-like inclusions – Eosinophilic granular bodies.

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