SEER Logo

SEER Training Modules

Brain & CNS Tumors

It is expected that more than 190,600 brain tumors will be diagnosed in the United States during 2003. Among these cases, there are about 40,600 primary brain tumors and 150,000 secondary (metastatic) brain tumors. In the United States, approximately 3,100 children younger than age 20 are diagnosed annually with brain tumors. Brain and CNS cancer is the leading cause of cancer-related death in patients younger than age 35 in this country.

Primary tumors are tumors that begin in the brain and tend to stay in the brain. Metastatic brain tumors begin as a cancer elsewhere in the body and spread, or metastasize, to the brain. Metastatic brain tumors are the most common brain tumor, with an annual incidence more than four times greater than that of primary brain tumors. The cancers that most commonly metastasize to the brain are breast and lung cancer.

Brain tumors are different from other cancers in several ways. One important factor is that brain tumors develop within the confined space of the skull where there is little extra room into which they may grow. Thus, even a small tumor can seriously affect normal brain function.

Also, brain tumors have relatively little tendency to metastasize outside the nervous system regardless of histologic type. Therefore, the terms "benign" and "malignant" have different meanings from those referring to abnormal growths elsewhere in the body. For brain tumor, benign means the tumor is relatively slow-growing; malignant means the tumor is aggressive or fast-growing. Most histologic types of CNS tumors can be either benign or malignant. Remember that a benign CNS tumor can become just as dangerous as a malignant one if the tumor presses on a vital area of brain tissue.

Go to Types of Brain and CNS Tumors to learn more about types of brain and CNS tumors.