Meningioma

Meningioma is the most common primary intracranial tumor, an extra-axial mass arising from the meningothelial (arachnoid cap) cells of the meninges. Most meningiomas are benign and slow-growing, displacing rather than infiltrating the brain, and their clinical behavior ranges from incidental lesions found by chance to atypical and malignant variants.

Definition

A meningioma is an extra-axial tumor arising from meningothelial (arachnoid cap) cells, attached to the dura and displacing adjacent brain; it is graded by the World Health Organization as grade 1 (benign), grade 2 (atypical), or grade 3 (malignant) according to histological and molecular features.

Scope

The entry covers meningioma as a tumor entity: its meningothelial origin and extra-axial growth, its WHO grading across benign, atypical, and malignant categories, its characteristic imaging appearance, and the place of observation, surgery, and radiation in its management spectrum. It is a reference description, not clinical guidance.

Core questions

• What distinguishes an extra-axial meningioma from intra-axial tumors on imaging and at surgery?
• How does WHO grading separate benign, atypical, and malignant meningiomas?
• When is observation appropriate versus surgical resection or radiation?
• How does tumor location govern the surgical approach and the risk of recurrence?

Key concepts

• Meningothelial (arachnoid cap) cell origin
• Extra-axial dural-based growth
• Dural tail sign
• WHO grade 1, 2, and 3
• Simpson grade of resection completeness
• Incidental and observed meningiomas
• Hormone-related growth influences

Mechanisms

Meningiomas grow from arachnoid cap cells of the meninges, forming a dural-based mass that compresses underlying cortex and cranial nerves as it enlarges, classically producing a broad dural attachment and a tapering dural tail on contrast imaging. Because they are extra-axial, a plane usually separates them from the brain, which influences resectability. Most are benign and slow-growing, but a subset show atypical or malignant histology with higher recurrence risk; the completeness of surgical removal, summarized historically by the Simpson grade, is associated with the likelihood of recurrence. The 2021 WHO classification incorporates molecular criteria alongside histology in grading.

Clinical relevance

Meningioma illustrates how a benign extra-axial tumor is recognized, graded, and reasoned about across a spectrum from incidental observation to operative management of higher-grade lesions. This entry describes the entity and its evidence base for educational orientation and is not a basis for individual diagnostic or treatment decisions.

Epidemiology

Meningioma is the most commonly reported primary central nervous system tumor in population-based registries, is more frequent in women than men, and increases in incidence with age; many are discovered incidentally on imaging performed for other reasons.

Evidence & guidelines

The EANO guideline by Goldbrunner and colleagues synthesizes diagnosis and management across meningioma grades, and the 2021 WHO classification provides the grading framework. Registry reports describe incidence and demographic distribution, and narrative reviews summarize the clinical spectrum.

History

Meningiomas were characterized by Harvey Cushing and Louise Eisenhardt in the early twentieth century, who coined the term and described their varied forms. Donald Simpson's mid-century grading of resection completeness linked surgical extent to recurrence, and successive WHO classifications, including the 2021 edition, refined histological and molecular grading.

Debates

How should small, asymptomatic meningiomas be managed?

Many incidental meningiomas are slow-growing and may be monitored, but deciding when growth or location warrants intervention rather than continued observation remains an individualized judgement discussed in guidelines.

What is the role of radiation after subtotal resection or in higher grades?

The benefit and timing of radiotherapy following incomplete resection or for atypical and malignant meningiomas continue to be evaluated, balancing recurrence risk against treatment morbidity.

Key figures

• Roland Goldbrunner
• Ian R. Whittle
• Donald Simpson
• David N. Louis

Seminal works

• whittle-2004
• goldbrunner-2021
• louis-2021

Frequently asked questions

Are meningiomas cancerous?

Most meningiomas are benign (WHO grade 1) and slow-growing, but a minority are atypical (grade 2) or malignant (grade 3) with a greater tendency to recur or behave aggressively.

Why are some meningiomas just watched rather than removed?

Because many are small, slow-growing, and cause no symptoms, monitoring with imaging can be appropriate; intervention is considered when a tumor grows, causes symptoms, or sits in a location of concern.