There are many types of primary brain tumors, which can be either benign (non-cancerous) or malignant (cancerous).
Cells from benign tumors rarely invade surrounding tissues and don’t spread to other parts of the body. However, benign tumors can press on sensitive areas of the brain and cause serious health problems and may become malignant. Malignant brain tumors are generally more serious and often are a threat to life. They can grow rapidly and crowd or spread to other parts of the brain or to the spinal cord. Malignant brain cancer cells rarely spread to other parts of the body.
Primary brain tumors are named according to the type of cells or the part of the brain in which they begin. For example, most primary brain tumors begin in glial cells. This type of tumor is called a glioma.
Among adults, the most common types of glioma are:
Astrocytoma: The tumor arises from star-shaped glial cells called astrocytes. It can be any grade. In adults, an astrocytoma most often arises in the cerebrum.
Meningioma: The tumor arises in the meninges. It can be grade I, II or III. It’s usually benign (grade I) and grows slowly.
Oligodendroglioma: The tumor arises from cells that make the fatty substance that covers and protects nerves. It usually occurs in the cerebrum. It’s most common in middle-aged adults. It can be grade II or III.
You can find more information about types of brain tumors here.
Osteoid osteoma, osteoblastoma, osteochondroma, giant cell tumor of the bone, aneurysmal bone cyst, eosinophilic granuloma and neurofibroma are the most common primary benign spine tumors. Primary benign tumors of the spine are more common than primary malignant tumors.
Doctors group tumors by grade. The grade of a tumor refers to the way the cells look under a microscope.
Grade I: The tissue is benign. The cells look nearly like normal brain cells, and they grow slowly.
Grade II: The tissue is malignant. The cells look less like normal cells than do the cells in a Grade I tumor.
Grade III: The malignant tissue has cells that look very different from normal cells. The abnormal cells are actively growing (anaplastic).
Grade IV: The malignant tissue has cells that look most abnormal and tend to grow quickly.
Cells from low-grade tumors (grades I and II) look more normal and generally grow more slowly than cells from high-grade tumors (grades III and IV). Over time, a low-grade tumor may become a high-grade tumor. However, the change to a high-grade tumor happens more often among adults than children.