Brain Tumor Health Article

Definition

A brain tumor is an abnormal growth of tissue, either malignant (cancerous) or benign (noncancerous), in the brain. Each year, more than 17,000 brain tumors are diagnosed in the United States.

Benign brain tumors

A benign brain tumor is composed of slow-growing noncancerous cells that never spread (by local extension or any other means) beyond the site where they originate. Common benign tumors are meningiomas, acoustic neuromas, pituitary gland tumors, craniopharyngiomas, germinomas, pinealomas, and hemangioblastomas. Even though a tumor is benign it may still be dangerous because, depending on its location, it may be inoperable and/or affect one or more brain functions.

Benign brain tumors have clearly defined borders, can often be removed completely, especially if they are on the brain's surface, and are unlikely to recur. Benign brain tumors do not infiltrate nearby tissues but as they continue to grow can cause severe pain, permanent brain damage, and death. Benign brain tumors sometimes become malignant.

Malignant brain tumors

A brain tumor is considered malignant if it contains cancer cells. Unlike other tumors, these spread by local extension and rarely metastasize beyond the brain. About half of all brain tumors are malignant.

Malignant brain tumors do not have distinct borders. They tend to grow rapidly, increase intracranial pressure, and metastasize to other parts of the brain or spinal cord. It is highly unusual for malignant brain tumors to spread beyond the central nervous system (CNS).

Primary brain tumors

Primary brain tumors originate in the brain. They represent about 1% of all cancers and 2.5% of all cancer deaths.

Metastatic or secondary brain tumors

Most brain tumors do not originate in the brain; they are metastases from other primary cancer sites. Approximately 25% of all cancer patients develop secondary or metastatic brain tumors when cancer cells spread from another part of the body. Secondary brain tumors are most apt to occur in patients who have melanoma, breast, colon, kidney, or lung cancer. Brain metastases can develop on any part of the brain or spinal cord.

Patient demographics

Primary brain tumors may develop at any age, but are most common in children between the ages of three and 12, and in adults aged 40–70. Primary brain cancer is the second-most common cause of cancer death between birth and the age of 34, and the third-most common cause of cancer death in men aged 35–54. Primary tumors of the brain and central nervous system are associated with AIDS in some patients.

Naming and grading brain tumors

A brain tumor's name describes its origin, how it grows, and the cell type it contains. A tumor in an adult is also graded or staged according to the extent or degree to which it is malignant; how rapidly it is growing, and how likely it is to invade other tissues; and how closely its cells resemble normal cells. (The less normal a tumor cell appears, the faster it is likely to grow.)

Low-grade tumors usually have well-defined borders. Some low-grade brain tumors form or are encapsulated (enclosed) in cysts. Low-grade brain tumors grow slowly, if at all. They may spread throughout the brain, but rarely metastasize to other parts of the body.

Mid- and high-grade tumors grow more rapidly than low-grade tumors; these tumors usually infiltrate healthy tissue. Their growth pattern makes it difficult to remove the entire tumor, and they recur more often than low-grade tumors.

A single brain tumor can contain several different types of cells. The tumor's grade is determined by the highest-grade (most malignant) cell detected under a microscope, even if most of the cells in the tumor are less malignant. An infiltrating tumor is a tumor of any grade that grows into surrounding tissue.