Most meningiomas are not cancer. Roughly 80% of these tumors are classified as benign (Grade 1), meaning they grow slowly, don’t invade surrounding brain tissue, and can often be cured with surgery alone. However, a smaller percentage are atypical (Grade 2) or malignant (Grade 3), and these higher-grade versions do behave like cancer, growing faster and carrying a real risk of returning after treatment.
The short answer, then, is that “meningioma” is not automatically a cancer diagnosis, but it’s not automatically harmless either. The grade matters enormously.
Where Meningiomas Come From
Meningiomas grow from cells in the meninges, the layered membranes that wrap around your brain and spinal cord. Specifically, they arise from arachnoid cap cells, which sit along the middle layer of the meninges. Because they start on the surface rather than inside the brain itself, most meningiomas push against the brain as they grow rather than infiltrating it. That distinction is one reason so many of them remain benign.
Even a benign meningioma can cause problems, though. As it slowly enlarges, it may press on nearby brain tissue, nerves, or blood vessels. Headaches, vision changes, hearing loss, seizures, or weakness in a limb can all develop depending on where the tumor sits. A small meningioma that never grows may never cause a single symptom and can be discovered by accident on a brain scan done for an unrelated reason.
How Grades Determine Whether It’s Cancer
The World Health Organization classifies meningiomas into three grades. This grading system was updated in 2021 to include, for the first time, molecular markers alongside traditional microscopic features.
Grade 1 (benign) meningiomas show fewer than 4 cell divisions per microscopic field and no invasion into brain tissue. These make up the large majority of cases. They grow slowly and, when fully removed, have a five-year recurrence-free survival rate around 95%.
Grade 2 (atypical) meningiomas show more active cell division (4 to 19 per field), brain invasion, or a combination of concerning microscopic features like areas of dead tissue within the tumor, unusually dense cell packing, or sheet-like growth patterns. They grow faster than Grade 1 tumors and are more likely to come back after surgery.
Grade 3 (anaplastic/malignant) meningiomas are true cancers. They divide rapidly (20 or more divisions per field), may look dramatically abnormal under a microscope, and can behave aggressively. Under the 2021 guidelines, certain genetic changes now automatically place a meningioma in Grade 3 regardless of how it looks under a microscope. Specifically, a mutation in the TERT promoter gene or the loss of both copies of tumor-suppressing genes called CDKN2A or CDKN2B bumps a meningioma to the highest grade.
Survival and Recurrence
Long-term survival depends heavily on the grade. Data from England covering diagnoses between 1999 and 2013 show that nearly 70% of people with a Grade 1 or Grade 2 meningioma survive 10 years or more. For Grade 3 meningiomas, that figure drops to about 40%.
Recurrence is the main long-term concern for all grades. Even among Grade 1 tumors, how completely the surgeon removes the tumor influences the odds. When the tumor, the attached membrane, and any involved bone are all removed, recurrence rates are lowest, around 5% at five years. When some tumor is intentionally left behind (because removing it would damage critical brain structures), recurrence at five years rises to roughly 19%. Modern imaging and radiation techniques have made these “incomplete” removals far more manageable than they once were, since leftover tumor can be closely monitored and targeted with focused radiation if it starts growing.
How Meningiomas Are Found
MRI with contrast dye is the primary tool. Meningiomas have a characteristic appearance: a well-defined, round or oval mass attached to the membrane lining the skull, often showing what radiologists call a “dural tail.” This is a visible thickening of the membrane that flares out from the edges of the tumor and tapers as it extends away. The dural tail sign has a specificity of about 94% for meningioma, meaning when it’s present, there’s a strong chance the tumor is a meningioma rather than something else. It’s not a guarantee, though. Other tumors can occasionally mimic this appearance, so biopsy or surgical removal is still needed for a definitive diagnosis and grading.
Treatment Options by Situation
Not every meningioma needs immediate treatment. For small, asymptomatic tumors discovered incidentally, the standard approach is observation with annual MRI scans. Many of these tumors grow so slowly that years can pass without any intervention. If the tumor is stable scan after scan, you may never need surgery.
Surgery becomes the first choice when a meningioma causes symptoms or shows growth on imaging. The goal is complete removal of the tumor along with its attached membrane, which gives the best chance of a cure for Grade 1 tumors. For tumors in surgically difficult locations, like the skull base, surgeons sometimes intentionally leave a small remnant behind rather than risk damaging critical nerves or blood vessels. That residual piece can then be treated with focused radiation.
Stereotactic radiosurgery, which delivers a precise, high-dose beam of radiation to a small target, is an alternative for tumors under a certain size, tumors in hard-to-reach locations, or patients who can’t safely undergo open surgery. It’s also used after incomplete surgery to treat whatever was left behind. For Grade 1 tumors, radiosurgery alone provides excellent long-term control.
Grade 2 and Grade 3 meningiomas typically require surgery followed by radiation therapy, since these tumors carry a much higher risk of returning.
Risk Factors
The main risk factors for meningioma are age (risk increases as you get older), being female, exposure to ionizing radiation, and a genetic condition called neurofibromatosis type 2. The female predominance, roughly two to one compared with men, has long pointed researchers toward a hormonal connection.
That connection was confirmed in a large population study looking at certain high-potency synthetic progestogens. Women who used these hormonal medications for more than a year had dramatically elevated risk. One drug, cyproterone acetate (used for conditions like severe acne, excessive hair growth, and as part of some hormonal therapies), carried an odds ratio of nearly 23 for prolonged users, meaning their meningioma risk was roughly 23 times higher than non-users. Two other potent progestogens showed elevated risk as well, though to a lesser degree. The association was dose-dependent: short-term use (under a year) showed only a slight increase, while prolonged use drove the risk sharply upward. Standard contraceptive pills at typical doses have not shown the same degree of association.
Prior radiation to the head, particularly in childhood, is the other well-established environmental risk factor. This includes therapeutic radiation for other cancers and, historically, lower-dose radiation that was once used to treat benign conditions of the scalp.