Brain Cancer

Clarification of the jargon
The term “brain cancer“ is commonly used, but can be a confusing term as it makes all brain cancers sound like one type of cancer. Brain cancer as a term actually encompasses a variety of cancers. There can be actual brain tumors which arise from the brain itself, known as primary brain cancers and of which there are several. There can also be brain metastases, which represent the spread of other cancers, such as lung or breast, to the brain.. Please see the section below on "What are brain tumors?" for more explanation.

What is the brain?
The brain is the organ in a person's skull that controls the functions of all of the other organs. Together, the brain and spine make up the central nervous system. The brain is responsible for the experience of the five senses (taste, touch, sight, hearing and smell). The brain is also the seat of thought, language, personality, creativity and memory. The brain controls movement, sensation, balance, and coordination. In order to do its job, the brain requires an enormous amount of the oxygen and nutrient energy that a person takes in regularly.
The brain is comprised of nerve cells (called neurons) which carry signals, and the cells which support the nerve cells (called glial cells ). There are a number of different types of glial cells, all with different names and functions. The glial cells outnumber the neurons in the brain by a ratio of 10:1

What are brain tumors?
Brain tumors occur when cells in the brain begin to divide out of control and start to displace or invade nearby tissues. Large collections of this "out of control" tissue are called tumors. Occasionally, brain tumors can spread throughout the body. Tumors that have the potential to spread to other sites of the brain or body are called malignant. When tumors start in the brain, they are called primary brain tumors. Any of the various normal cell types of the brain can mutate and become a primary tumor, and the particular cell type which makes up the tumor controls how the tumor is likely to behave. Brain tumors are not really thought of as a single disease, but rather as a collection of several diseases that are characterized by the cell type that makes them up, by how they behave, and by how they are treated. One of the special characteristics of brain tumors is that benign (non-cancerous) tumors in the brain can be just as bad as malignant (cancerous) brain tumors. This is because the brain is such an important organ. It is locked into place by the skull and can't move out of the way if a tumor is growing near it. Even a benign tumor can cause pressure on the brain, and this pressure can be both symptomatic and life-threatening.
The brain is also a frequent site of metastases. Metastases are tumors which have spread from a cancer that started in a different body part; they do not start in the brain, but instead take up residence there after traveling from a separate cancer (like a lung cancer or breast cancer). These are not classified as primary brain tumors, but instead as brain metastases.

How are brain tumors classified?
Brain tumors are classified by the both the cell of the brain that makes them up, and how the tumor looks under a microscope. Primary brain tumors can arise from any of the cells in the brain. They can come from the neurons, the glial cells, the lining of the brain, or from specific structures in the brain. Glial cells support the neurons of the brain and tumors which arise from these cells are known as glial tumors. The membrane that surrounds the brain can also develop tumors and these are known as meningiomas. There are other types of tumors, which involve other structures of the brain including ependymomas among others. Metastases can travel from a variety of different cancer types. When a special type of doctor (called a pathologist ) looks at brain tumors under a microscope, he/she can get a sense of how aggressive the tumor is by the way the cells look.