Although such growths are popularly called brain tumors, not all brain tumors are cancer. Cancer is a term reserved for malignant tumors. Malignant tumors can grow and spread aggressively, overpowering healthy cells by taking their space, blood, and nutrients. They can also spread to distant parts of the body. Like all cells of the body, tumor cells need blood and nutrients to survive. Tumors that do not invade nearby tissue or spread to distant areas are called benign. In general, a benign tumor is less serious than a malignant tumor. But a benign tumor can still cause many problems in the brain by pressing on nearby tissue.

  Types of Brain Cancer

•  Brain tumors are abnormal growths of cells in the brain.
  
  
• Although such growths are popularly called  brain tumors , not all brain tumors are cancer. Cancer is a term reserved for malignant tumors.
• Malignant tumors can grow and spread aggressively, overpowering healthy cells by taking their space, blood, and nutrients. They can also spread to distant parts of the body. Like all cells of the body, tumor cells need blood and nutrients to survive.
• Tumors that do not invade nearby tissue or spread to distant areas are called benign.
• In general, a  benign tumor  is less serious than a malignant tumor. But a benign tumor can still cause many problems in the brain by pressing on nearby tissue.
• In the U.S., brain or nervous system tumors affect about 6 of every 1,000 people.

Primary Brain Cancers

• The brain is made up of many different types of cells.
• Some brain cancers occur when one type of cell transforms from its normal characteristics. Once transformed, the cells grow and multiply in abnormal ways.
• As these abnormal cells grow, they become a mass, or tumor.
• The brain tumors that result are called primary brain tumors because they originate in the brain.
• The most common primary brain tumors are gliomas,  meningiomas , pituitary adenomas, vestibular schwannomas, and primitive neuroectodermal tumors (medulloblastomas). The term glioma includes glioblastomas, astrocytomas, oligodendrogliomas, and ependymomas.
• Most of these are named after the part of the brain or the type of brain cell from which they arise.

Metastatic Brain Cancer

Metastatic brain tumors are made of cancerous cells from a tumor elsewhere in the body. The cells spread to the brain from another tumor in a process called metastasis. This is the most common type of brain tumor. 

Causes of Brain Cancer

As with tumors elsewhere in the body, the exact cause of most brain cancer is unknown. Genetic factors, various environmental toxins,  radiation  to the head, HIV infection, and cigarette  smoking  have all been linked to cancers of the brain. In most cases, no clear cause can be shown.