Brain Tumor Types

Brain tumors are classified as either “primary” or “metastatic.” Primary brain tumors originate in the brain and may spread within the central nervous system (brain and spinal cord). They rarely spread to other parts of the body. There are many different types of primary brain tumor. Some are aggressive and pose an immediate risk to the patient’s health, while some are slow-growing and may not need to be treated right away.

Metastatic brain tumors originate from a cancer in another organ and spread to the brain. For treatment, all brain tumors are classified by the type of cell the tumor resembles, the location of the tumor, whether it is well-circumscribed versus diffuse in nature, the grade of the tumor (WHO grading schema), and increasingly, the molecular or genetic features of the tumor.

At Siteman Cancer Center, our Washington University oncologists and neurosurgeons will identify your tumor correctly and develop a treatment plan tailored to you.

Glioblastoma and other gliomas

Glioblastomas (WHO Grade IV): Glioblastomas are the most common, primary malignant brain tumors in the adult population but can be seen in any age group. These tumors are challenging to treat even with multidisciplinary treatments (surgery, radiation therapy, and chemotherapy). Improving patient outcomes through clinical trials is an important aspect of the treatment of these tumors. IDH1 mutation can sometimes be seen in these tumors, often in younger adults, and is a relatively favorable marker in terms of prognosis.

Diffuse astrocytomas (WHO Grade II and III): These tumors grow slowly but are infiltrative, which makes it difficult to remove these tumors completely. They therefore require adjuvant therapy in many cases. They also tend to progress to a higher grade—Grade III tumors are called anaplastic astrocytoma, which is associated with faster growth, and occur most often in young adults (30-40 years of age). The IDH1 mutation is often seen in these tumors.

Oligodendrogliomas (WHO Grade II and Grade III): They occur most often in young adults and have infiltrative properties but tend to do better than astrocytomas because the associated molecular alterations (chromosome 1p and 19q co-deletions) appear to make them more slow growing and responsive to therapy. In addition, the IDH1 mutation is almost always seen in these tumors. Grade III tumors are called anaplastic oligodendroglioma.

Pilocytic astrocytomas (WHO Grade I): They grow slowly, are well circumscribed and therefore respond well to surgical resection. Recurrences are rather infrequent in these tumors. These tumors occur more often in children and young adults as compared to older adults.

Ependymomas can be WHO Grades I through III. WHO Grade I tumors are also called sub-ependymomas in the brain and myxopapillary ependymomas in the spinal cord; they generally grow slowly and can often be removed completely by surgery. WHO Grade II tumors are however more common and are often seen in the posterior fossa. These also respond well to surgical resection given their well-circumscribed nature. Sometimes these tumors can undergo malignant transformation and become WHO Grade III anaplastic ependymomas. Adjuvant therapy is required in these patients.

Additional glioma types also exist, and, as mentioned above, are increasingly classified by their molecular or genetic characteristics, such as ganglioglioma and diffuse midline glioma.

Learn more about glioblastoma.

Learn more about other gliomas.


Meningiomas arise in the meninges and more commonly occur in women. They are the most common primary brain tumors—greater than 33% of all primary brain tumors.

WHO Grade I meningiomas are slow-growing and benign.

WHO Grade II and III meningiomas have more aggressive clinical behavior because of their tendency to recur. WHO Grade III meningiomas are also associated with increased mortality and are more common in men.

Learn more about meningiomas.

Pituitary tumors

Pituitary adenoma is a very common benign intracranial tumor seen in adults and is thought to occur in as many as 1 in 6 people. It can be functional (with endocrine symptoms and signs) or nonfunctional, or it can be micro- or macro-adenoma depending on its size (less than or greater than 1 cm, respectively). Functional ones tend to present earlier because of their endocrine symptoms and therefore are usually small at the time of presentation. In contrast, nonfunctional ones tend to present as macroadenomas with visual deficits. Surgical resection is often the frontline treatment for growing nonfunctional adenomas and many functional adenomas. Medical treatment plays an important role, particularly in prolactinomas, where it is considered frontline, but other functional adenomas may also benefit from medical therapy. Radiation therapy can also be an option.

Learn more about pituitary tumors.

Vestibular schwannoma (Acoustic neuroma)

These are benign tumors which form on the vestibular nerve and look like growths of Schwann cells, which normally support peripheral nerves.

Learn more about vestibular schwannomas.

Metastatic brain tumors

Metastatic brain tumors originate from a cancer in another organ and spread to the brain. The types of cancer that commonly spread to the brain are cancers of the lung, breast, skin (melanoma), and colon. These can present as solitary or multiple brain lesions. Treatment is variable and should be tailored to the specific patient, ranging from surgery to radiation therapy to medical treatment.

Learn more about cancers that have spread to the brain.