atypical meningioma

atypical meningioma

A meningioma with a worse prognosis than typical meningiomas, which is characterised by cytologic atypia, increased cellularity, small cells with high nuclear:cytoplasmic ratios, prominent nucleoli, patternless or sheet-like growth, patchy necrosis, and ≥ 4 mitoses/10 HPFs.
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Twenty-seven cases of WHO grade I meningiomas would have increased in grade to atypical meningiomas (WHO grade II), and one atypical meningioma would have increased to anaplastic meningioma (WHO grade III).
Histopathology and MIB-1 labeling index predicted recurrence of meningiomas: a proposal of diagnostic criteria for patients with atypical meningioma.
Similar to atypical meningiomas, recurrence can be local or distant and may have a mortality rate of up to 23%.
Anaplastic meningiomas (WHO grade 3) account for <1% all meningiomas and have a much shorter mean survival time, with a 5-year-survival rate of approximately 64%, compared with 95% for atypical meningiomas (2).
Two tumors (4%) were atypical meningiomas with increased mitotic activity.

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