Meningioma

Meningioma a very common tumour in neuropathology.

General

Prevalence

• Common.

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 WTC):

• Whorled appearance - key feature.
• Thick-walled blood vessels, usually prominent.
• Calcification.

Many subtypes exist:

• Atypical meningioma.
  • Has invasion of the brain - WHO Grade 2.
• Angiomatous meningioma.
• Others.

Images:

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

Notes:

• May involute into benign sclerotic tissue.

Histomorphologic grading

Grading:

• Grade 1:
  • Low mitotic rate.
  • Excludes clear cell, chordoid, papillary, and rhabdoid subtypes.
• Grade 2 (either #1 or #2):
  1. Brain-invasive meningioma.
     • Protrusion of meningioma into brain.
       • Meninogioma with entraped GFAP +ve tissue.
  2. Atypical meningioma (by histomorphology).
     • Intermediate mitotic rate (>= 4 mitoses/10 HPF - for whatever HPF means, see HPFitis.)
     • 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.
• Grade 3 (either of the following):
  • High mitotic rate (>=20 mitoses/10 HPF - for whatever HPF means, see HPFitis.)
  • "Frank anaplasia"; marked nuclear atypia.

Notes:

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

IHC

• EMA +ve.
  • Other CKs usu. -ve.

See also

• Neuropathology.
• Neurohistology.
• CNS tumours.