A brain tumor is an uncontrolled growth of cells that form a mass in the brain. It may noncancerous (benign) or cancerous (malignant). A benign brain tumor has no cancerous cells and does not invade adjacent tissue. Its size and location may cause some symptoms as it presses on vital areas. Malignant brain tumors, which contain cancer cells, invade tissue that surrounds them, usually growing quickly. Sometimes malignant tumors will recur following treatment, but seldom spread throughout the body.
A brain tumor may be a new growth or a congenital condition (present at birth). If a tumor forms in the brain, it is called a primary brain tumor. Tumors that spread to the brain from other parts of the body are referred to as secondary brain tumors or metastic brain tumors. Even though the cancers may be in the brain, they are still treated based on the original type, for example lung cancer or breast cancer.
In addition to metastic brain tumors, science has classified many types of brain tumors, including:
- Gilomas, the most common form of primary brain tumors
- Meningiomas that form in the outer covering of the brain
- Schwannomas on nerves usually in the inner ear
- Pituitary tumors are deeply located under the brain
- Primitive neuroectodermal tumors, more common in children than adults
- Medulloblastomas in the cerebellum
- Craiopharyngiomas, benign tumors on the base of the brain, eye nerves and the pituitary gland
- Pineal region tumors on the pineal gland, deeply located in the middle of the brain
- Germ cell tumors, a malignant tumor also found in near the pineal gland