The most common type of primary brain tumor is a meningioma, a slow-growing mass that forms in the protective layers surrounding the brain. In adults over 40, meningiomas occur at a rate of about 23 per 100,000 people per year, far outpacing every other type. But the answer shifts depending on whether you’re asking about cancerous or noncancerous tumors, and which age group you’re looking at.
Primary vs. Metastatic Brain Tumors
Before breaking down tumor types, it helps to know there are two broad categories. Primary brain tumors start in the brain itself. Metastatic (or secondary) brain tumors start somewhere else in the body, most often the lungs, breast, or skin, and spread to the brain. Metastatic tumors are actually far more common overall: more than 200,000 people are diagnosed with brain metastases each year in the U.S., compared to roughly 25,000 new primary brain tumors. When people ask about “the most common brain tumor,” though, they’re usually asking about tumors that originate in or around the brain, so that’s the focus here.
Meningiomas: The Most Common Overall
Meningiomas grow from the meninges, the three-layered membrane that covers and protects the brain just under the skull. They’re almost always noncancerous. About 81% are classified as the lowest grade (WHO grade I), meaning they grow slowly and rarely spread. Roughly 19% fall into grade II, which is somewhat more aggressive, and grade III meningiomas are rare enough that large studies often exclude them entirely.
Because meningiomas grow on the surface of the brain rather than inside it, many are discovered incidentally during a scan for something else entirely. Small, slow-growing meningiomas may never cause symptoms and can simply be monitored with periodic imaging. Larger ones can press on nearby brain tissue, causing headaches, vision changes, weakness, or seizures depending on their location. When treatment is needed, surgery is the primary approach, and the outlook is generally favorable since most meningiomas don’t come back after complete removal.
Meningiomas are roughly twice as common in women as in men, a pattern researchers believe is influenced by hormonal factors. Risk increases with age, peaking in adults over 65.
Glioblastoma: The Most Common Cancerous Type
If you narrow the question to malignant brain tumors, the answer changes. Glioblastoma is the most common primary brain cancer, accounting for about 14% of all primary brain tumors. It arises from glial cells, the supportive tissue of the brain, and is classified as the highest grade (WHO grade IV). Unlike meningiomas, glioblastomas grow within the brain tissue itself, making them far harder to treat.
Glioblastomas are aggressive. With standard treatment, the median life expectancy after diagnosis is about 12 to 18 months. Only 5% to 7% of people are alive five years later. These tumors grow quickly, can infiltrate surrounding brain tissue in ways that make complete surgical removal nearly impossible, and tend to recur even after treatment. Symptoms often develop over weeks and can include worsening headaches, personality changes, nausea, and new-onset seizures.
Glioblastoma is most common in older adults, typically appearing between ages 55 and 70, and occurs slightly more often in men.
How Common Types Vary by Age
The most common brain tumor type shifts significantly across age groups. In younger adults between 15 and 39, pituitary tumors are the leading type, occurring at a rate of about 4.65 per 100,000 people per year. These typically noncancerous growths form in the pituitary gland at the base of the brain and often cause hormonal imbalances before they’re large enough to create pressure symptoms. Many are treatable with medication alone.
In adults over 40, meningiomas dominate, as described above. In children, the picture is different again. The most common childhood brain tumors include pilocytic astrocytomas (a low-grade type of glioma), medulloblastomas, and other malignant gliomas. Unlike in adults, where noncancerous tumors far outnumber cancerous ones, a larger share of pediatric brain tumors are malignant. Pilocytic astrocytomas, however, tend to be slow-growing and have a good long-term prognosis with treatment.
The Big Picture on Brain Tumor Numbers
Across all ages and types, about 26 out of every 100,000 people in the U.S. are diagnosed with a primary brain or central nervous system tumor each year. That five-year total comes to nearly 490,000 cases. The vast majority of those, roughly 74%, are noncancerous. That’s an important number, because the phrase “brain tumor” tends to evoke worst-case scenarios, when in reality most primary brain tumors are not cancer.
Malignant brain tumors account for about 6.86 per 100,000, or around 129,000 cases over a five-year period. So while any brain tumor diagnosis is serious and deserves medical attention, the odds strongly favor a noncancerous type, particularly in adults. The specific type, grade, size, and location all shape what treatment looks like and what you can expect going forward.