From the Guidelines
Meningiomas are classified primarily by their histological grade and location, with the World Health Organization (WHO) classifying them into three grades based on their aggressiveness and likelihood of recurrence, as recently clarified in the cIMPACT-NOW update 8 1. The classification of meningiomas is crucial for determining treatment approaches and predicting patient outcomes.
- The WHO classification system categorizes meningiomas into three grades: Grade I (benign), Grade II (atypical), and Grade III (malignant) 1.
- Grade I meningiomas are slow-growing and account for about 80% of all meningiomas, while Grade II and III meningiomas have higher recurrence rates and poorer prognoses 1.
- Meningiomas are also classified by their location in the brain, including convexity, parasagittal, sphenoid wing, olfactory groove, tuberculum sellae, cerebellopontine angle, and spinal meningiomas 1.
- The cIMPACT-NOW update 8 provides recommendations for the use of molecular testing to inform grading and diagnosis, including the use of next-generation sequencing and copy-number assessment 1.
- The update also highlights the importance of considering molecular data, such as chromosome 1p deletion and NF2 oncogenic variant, in assigning a grade to meningiomas 1.
- Additionally, the update suggests that brain-invasive but otherwise morphologically benign (BIOB) meningiomas should not be graded before molecular data are obtained, and that cases with borderline morphological grading criteria should undergo additional molecular testing 1. Key points to consider in the classification and grading of meningiomas include:
- The use of molecular testing to inform diagnosis and grading
- The consideration of chromosome 1p deletion and NF2 oncogenic variant in assigning a grade
- The importance of location in the brain in determining treatment approaches and predicting patient outcomes
- The need for further studies to fully understand the prognostic significance of molecular markers and to develop more effective treatment strategies for meningiomas 1.
From the Research
Meningioma Classification
Meningiomas are classified into different grades based on their histological features. The World Health Organization (WHO) classifies meningiomas into three grades:
- Grade I: Benign meningiomas
- Grade II: Atypical meningiomas
- Grade III: Anaplastic or malignant meningiomas 2, 3, 4
Histological Features
The classification of meningiomas is based on various histological features, including:
- Cell morphology and arrangement
- Mitotic index
- Presence of necrosis or brain invasion
- Expression of certain proteins, such as MIB-1 and p53 3, 5
Prognostic Factors
Several prognostic factors have been identified for meningiomas, including:
- Histological grade: Higher grades are associated with a poorer prognosis 6
- Age: Younger patients tend to have a better prognosis 6
- Extent of resection: Complete resection is associated with a better prognosis 6
- MIB-1 labeling index: Higher indices are associated with a poorer prognosis 5
Molecular Characteristics
Recent studies have identified certain molecular characteristics that may be associated with the development and progression of meningiomas, including: