Meningioma

Meningioma a very common tumour in neuropathology.

General

Prevalence

• Common.
• May be caused by prior radiation.

Radiology

• Extra-axial.

Prognosis

• Most are benign.
  • May be malignant.

Genetics

• May be seen in genetic disorders such as:
  • Neurofibromatosis 2 (NF2).
  • Nevoid basal cell carcinoma syndrome (Gorlin syndrome).
  • Cowden syndrome.

Microscopic

Features (memory device WC):

• Whorled appearance - key feature.
• Calcification, psammomatous (target-like appearance; (tight) onion skin).

Images:

• Meningioma - high mag. (WC).
• Meningioma - intermed. mag. (WC).
• Meningioma (neuropathologyweb.org).
• Meningioma with brain invasion - intermed. mag. (WC).
• Meningioma with brain invasion - high mag. (WC).

Notes:

• May involute into benign sclerotic tissue.
• Thick-walled blood vessels = feature of schwannoma.

Morphologic subtypes

• Many subtypes exist.
• The histologic subtypes generally don't have much prognostic significance.
  • Some subtypes are high grade by definition; also see histologic grading.

Grade I

• Meningothelial.
  • Most common.
  • Microscopic: syncytial, nuclear clearing (pseudoinclusions).
• Fibrous (fibroblastic).
  • Not collagen but looks like it. (It is really laminin or fibronectin).
• Transistional.
  • Rare.
• Psammomatous.
  • Microscopic: Psammoma bodies.
• Angiomatous (vascular).
  • May bleed like stink.
• Microcystic.
  • Microscopic: cystic appearance.
• Secretory.
  • Microscopic: intracytoplasmic inclusions that are CEA +ve and PAS +ve.
  • Assoc. with brain edema; may have a worse outcome.
• Lymphoplasmacyte-rich.
• Metaplastic.
  • Much talked about... but very rare.
  • Microscopic: cartilage or bone formation.

Grade II

• Invasive (invades the brain).
• Clear cell.
  • Microscopic: clear cells - contain glycogen (PAS +ve).
  • Epi.: usu. spinal cord.
• Chordoid (chordoma-like).
  • Microscopic: myxoid appearance.

Grade III

• Papillary.
  • Microscopic: true papillae.
• Rhaboid.
  • Microscopic: rhadoid appearance (abundant cytoplasm).

Histologic grading

Grading:

• Grade 1:
  • Low mitotic rate (< 4 mitoses/10 HPF - for whatever HPF means, see HPFitis).
  • Excludes clear cell, chordoid, papillary, and rhabdoid subtypes.
• Grade 2 (either #1, #2 or #3):
  1. Brain-invasive meningioma.
     • Protrusion of meningioma into brain.
       • Meninogioma with entraped GFAP +ve tissue.
  2. Atypical meningioma (by histomorphology) - either A or B.
     • A. Intermediate mitotic rate (>= 4 mitoses/10 HPF - for whatever HPF means, see HPFitis.)
     • B. Three of the following five features:
       1. Sheeting architecture.
       2. High NC ratio clusters; clusters of "lymphocyte-like" cells.
       3. Hypercellularity.
       4. Macronucleoli.
       5. Necrosis not caused by treatment, e.g. radiation or embolization.
  3. Clear cell or chordoid subtype.
• Grade 3 (either of the following):
  • High mitotic rate (>=20 mitoses/10 HPF - for whatever HPF means, see HPFitis.)
  • "Frank anaplasia"; marked nuclear atypia.
  • Papillary or rhabdoid subtype.

Notes:

• Grade II soft criteria memory device HMNs: hypercellular, macronucleoli, NC ratio increased, necrosis, sheeting.

IHC

• EMA +ve.
• Other CKs usually -ve.

DDx of meningioma & IHC

• S-100 +ve - schwannoma.
  • +ve in ~80% of fibrous meningiomas.
• CD34 +ve - solitary fibrous tumour.
  • +ve in ~60% of fibrous meningiomas.
• EMA +ve in ~30% of hemangiopericytoma.
• Claudin-1 - new kid on the block: +ve in meningioma, but low sensitivity.

Standard work-up (UHN)

• Ki-67 >5-10% - predicts re-occurrence.
• PR (progesterone receptor) +ve in 2/3; -ve PR predicts re-occurrence.

See also

• Neuropathology.
• Neurohistology.
• CNS tumours.

External links

• Histopathology review of meningioma (medscape.com).