Types of Brain Tumors: Gliomas and More

A brain tumor is a growth of abnormal cells in the brain or spinal cord. That word alone does not tell you whether it is cancer. Some brain tumors are benign, meaning they do not spread to other parts of the body. But even a benign tumor can cause serious problems, because it grows inside a closed space with no room to expand. Location and behavior often matter as much as whether a tumor is technically cancer.

Gliomas make up about 3 in 10 brain tumors. They start in glial cells, which normally support and protect nerve cells. Gliomas come in several forms.

Astrocytomas are the most common glioma. Low-grade astrocytomas grow slowly. The highest-grade form, called glioblastoma, is the most aggressive and most common malignant brain tumor in adults.

Oligodendrogliomas make up only 1% to 2% of brain tumors. Most are a slower-growing grade, though they still spread into nearby brain tissue. Faster-growing forms exist too.

Ependymomas make up about 2% of brain tumors. They tend to grow in the fluid-filled spaces of the brain, called ventricles, or in the spinal cord. They range from slow to fast growing. Because of where they sit, they can block the normal flow of fluid around the brain, causing a buildup called hydrocephalus.

Meningiomas grow in the layers of tissue that cover the brain and spinal cord, not in brain tissue itself. They make up about a third of primary brain tumors, making them very common. Most meningiomas are grade 1, meaning benign and slow-growing. A smaller number are grade 2, called atypical, or grade 3, which is malignant and grows faster. Many grade 1 meningiomas are found by chance on a scan done for another reason and never need treatment at all — just monitoring.

Schwannomas grow from the cells that insulate nerves. They are generally benign. When one grows on the nerve responsible for hearing and balance, it is called a vestibular schwannoma or acoustic neuroma. These can cause hearing loss or balance trouble as they grow, even though they are not cancer.

Pituitary tumors grow in the pituitary gland, a small structure that controls many of the body's hormones. These are almost always benign. Even so, they can cause real problems — either by growing large enough to press on nearby structures like the optic nerves, or by producing excess hormones that disrupt the body.

Primary central nervous system lymphoma is a cancer of immune cells that starts in the brain itself. It is uncommon, making up about 2% of primary brain tumors, but it tends to grow quickly. Metastatic brain tumors are different: they are not primary brain tumors at all, but cancer that started somewhere else in the body — commonly the lung, breast, or skin — and spread to the brain. In adults, these are actually more common than tumors that start in the brain itself.

Two people can both hear the words "brain tumor" and be facing entirely different situations. A grade 1 meningioma that needs only monitoring is not the same conversation as a glioblastoma. Knowing the specific type, and its grade, is what turns a frightening general term into a concrete plan.

• What specific type of tumor do I have, and what grade is it?
• Is this tumor considered benign or malignant, and what does that mean for my situation specifically?
• Does this tumor need treatment now, or can it be monitored?
• What symptoms would mean I need to be seen sooner than my next scheduled visit?

• American Cancer Society — Types of Brain Tumors and Spinal Cord Tumors in Adults