Meningioma

Epidemiology:

•  Adults predominantly

Common sites:

• dural-based or ventricular-based
• arachnoid granulations
• parasagittal
• lateral convexity
• wing of sphenoid
• olfactory groove
• sella turcica
• foramen magnum
• spine (F:M = 10:1)
• not midline

Gross features:

• solitary
• multiple suggests NF2
• rounded
• cut section looks like a potato
• compressing underlying brain but usually easily separable from brain
• extension into bone maybe
• thin capsule usually
• bosselated or polypoid maybe
• en plaque variant of growth:
• sheetlike spread along the surface of the dura
• firm and fibrous to finely gritty
• extremely calcified maybe

Histologic features:

• whorling pattern is hallmark (not pathognomonic, not always present)
• very heterogenous appearances
• syncytial pattern:
• whorled clusters of cells in tight groups without visible cell membranes
• fibroblastic pattern:
• elongated cells
• abundant collagen deposition between cells
• Transitional pattern:
• Features of syncytial and fibroblastic pattern
• Psammomatous pattern:
• Numerous psammoma bodies
• secretory variant:
• PAS-positive globules
• Intracellular lumens by EM
• Microcystic  pattern:
• Losse, spongy architecture
• Chordoid variant:
• Appearance similar to chordoma
• Grade II by definition
• Clear cell variant:
• Grade II by definition
• Papillary variant:
• Pleomorphic cells arranged around fibrovascular cores
• Grade III by definition
• Rhabdoid variant:
• Sheets of tumour cells with hyaline eosinophilic cytoplasm (containing intermediate filaments)
• Grade III by definition
• Xanthomatous degeneration common
• Metaplasia
• Often osseus
• Nuclear pleomorphism
• Moderate nuclear pleomorphism is common
• Grading (WHO – 4 grades):
• Not increased by invasion of: bone, soft tissue, brain
• WHO Grade II (atypical meningioma)
• >= 4 mitoses / 10 HPF, OR
• Three or more atypical features:
1. Increased cellularity
2. Small cells with high n:c ratio
3. Prominent nucleoli
4. Patternless growth
5. Necrosis
• WHO Grade III – anaplastic (malignant) meningioma
• Appearance of high-grade sarcoma
• Some evidence of meningothelial origin
• Mitotic rate > 20 / 10HPF often
• MIB-1 index is not part of grading but is an independent factor for grade I/IV

Immunophenotype:

Marker:	Sensitivity:	Specificity:
EMA	commonly
PR	often
PAS (globules in secretory variant)
CK (secretory variant)
CEA (secretory variant)

Molecular features:

• Sporadic:
• 22q loss is most common cytogenetic abnormality
1. NF2 gene (22q12) is likely candidate
2. more common in fibroblastic or transitional histology
• NF2 mutations (50-60%)
1. absence of function mutations
2. more common in fibroblastic or transitional histology
• Familial:
• NF2

Other features:

• radiology:
• brightly enhancing (vascular)
• prognosis:
• benign predominantly
• WHO grade II (atypical meningiomas) – higher rate of recurrence
1. more aggressive local growth

• WHO Grade III – anaplastic (malignant) meningioma – highly aggressive
• High rate of recurrence
• Invasion of brain (either with broad pushing edge or single cells
• Increased risk of recurrence
• Rapid growth during pregnancy has been reported

References:

•  Robbins & Cotran Pathologic Basis of Disease (2005)