A brain tumor starts in one cell that becomes abnormal due to changes in the cellular DNA. Many tumors that are called brain tumors do not occur in the brain itself. A primary brain tumor can occur in the brain itself, or in the cranial nerves, meninges, skull, pituitary gland or pineal gland.
A metastatic brain tumor is spread from a cancer in another part of the body. Metastatic brain tumors most often lodge in the brain tissue, but can occur in the skull or inner lining of the skull (dura).
Meningiomas- The meninges are layers that help separate the skull from the brain. Meningeal tumors usually grow slowly and only 1% are malignant. When malignant, they do not spread to other areas of the body but can be locally aggressive.
Gliomas - Solid tumors that arise from glial cells. Glial cells help support the function of the neurons (electrically active in brain cells). Glial cells include astrocytes, oligodendrocytes and ependymal cells.
Gliomas are divided into 2 categories:
Acoustic Neuroma - Also called vestibular schwannomas- These are benign tumors that grow from a cranial nerve in the brain, the vestibular nerve, but can often affect the hearing nerve (acoustic nerve).
Chondroma - A very rare benign tumor made of bone cartilage found in the skull. The skull base and the paranasal sinuses contain cartilage. Chondromas can develop into this cartilage and are more common in people from the ages of 10 to 30. Chondromas grow slowly but can cause the bone to fracture. If they grow large enough, they can create pressure on the brain. Surgery is the most common treatment for chondromas.
Chondrosarcoma - A malignant bone cancer that mostly affects cartilage. It can start in the skull base. It is the second most common type of bone cancer and most often occurs in people between the ages of 50 and 70. Surgery is the most common treatment for chondrosarcomas and radiation therapy may be performed after surgery.
Chordoma - A rare malignant and slow-growing tumor that is classified as a bone tumor. Less than 1% of all primary brain tumors are chordomas. The intracranial chordoma is a skull base tumor that can infiltrate and erode the sphenoid and basiocciput and can spread into the petrous bones, the paranasal sinuses, the sella turcica and the cavernous sinuses. They are malignant, however, it is usually impossible to excise the cranial tumors completely and tend to recur.
CNS Lymphoma - A type of non-Hodgkin's lymphoma that is more commonly seen in immunocompromised patients but is also seen in patients with an intact immune system.
Metastatic brain tumors are the most common brain tumors in adults and account for 50% of all brain tumors. Metastatic brain tumors occur in 25% of all cancer patients.
Incidence of Brain Metastasis According to Primary Site