Brain cancer - What is brain cancer ?

What is Brain cancer ?

Brain cancer is  the consequence of abnormal growths of cells in the brain. Brain cancers can arise from primary brain cells, the cells that form other brain components (for example, membranes, blood vessels), or from the growth of cancer cells that develop in other organs and that have spread to the brain by the bloodstream (metastatic brain cancer).

Knowing of brain cancer or brain tumors :

• Although many growths in the brain are popularly called brain tumors, not all brain tumors are cancerous. Cancer is a term reserved for malignant tumors. 
• Malignant tumors grow and spread aggressively, overpowering healthy cells by taking their space, blood, and nutrients. Like all cells of the body, tumor cells need blood and nutrients to survive. This is especially a problem in the brain, as the added growth within the closed confines of the skull can lead to an increase in intracranial pressure or the distortion of surrounding vital structures, causing their malfunction. 
• Tumors that do not grow aggressively are called benign. Almost all tumors that begin in the brain do not spread to other parts of the body. The major difference between benign and malignant tumors is that malignant tumors can invade the brain tissues and grow rapidly. This rapid growth in the confines of the skull can quickly cause damage to nearby brain tissue. 
• In general, a benign tumor is less serious than a malignant tumor. However, a benign tumor can still cause many problems in the brain, but usually the problems progress at a slower rate than malignant tumors. 

Sometimes people confuse brain aneurysms with brain tumors. Brain aneurysms are not tumors; they are areas in the brain arteries or veins that are abnormally weak and expand to form a ballooning or expansion of the vessel wall. They seldom produce any symptoms unless they begin to leak blood into the surrounding brain tissue. Aneurysms may be congenital (present at birth) or expanded or formed in brain vessels after vessel damage (for example, trauma, atherosclerosis, high blood pressure) but are not formed from cancer cells. Unfortunately, when aneurysms produce symptoms, they can resemble those produced by brain tumors.

Primary brain tumors

Primary brain tumor is The brain that  made up of many different types of cells and tumors that arise from a brain cell type .

• Cancers occur when one type of cell transforms and loses its normal characteristics. Once transformed, the cells grow and multiply in abnormal ways.
• As these abnormal cells grow, they become a mass of cells, or tumor. 
• Brain tumors that result from this transformation and abnormal growth of brain cells are called primary brain tumors because they originate in the brain.

The most common primary brain tumors are gliomas, meningiomas, pituitary adenomas, vestibular schwannomas, primary CNS lymphomas, and primitive neuroectodermal tumors (medulloblastomas). The term glioma is an expansive one since it includes numerous subtypes, including astrocytomas, oligodendrogliomas, ependymomas, and choroid plexus papillomas.

These primary tumors are named after the part of the brain or the type of brain cell from which they arise. Brain tumors vary in their growth rate and ability to cause symptoms. The cells in fast growing, aggressive tumors usually appear abnormal microscopically.

According to The National Cancer Institute (NCI) uses a grading system to classify tumors. The NCI lists the following grades:

• Grade I: The tissue is benign. The cells look nearly like normal brain cells, and cell growth is slow.
• 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. These abnormal-appearing cells are termed anaplastic. 
• Grade IV: The malignant tissue has cells that look most abnormal and tend to grow very fast. 

Metastatic brain tumors

Metastatic brain tumors are made of cancerous cells that spread through the bloodstream from a tumor located elsewhere in the body. The most common cancers that spread to the brain are those arising from cancers that originate in the lung, breast, and kidney as well as malignant melanoma, a skin cancer. The cells spread to the brain from another tumor in a process called metastasis. The process metastasis occurs when cancer cells leave the primary cancer tissue and enter either the lymphatic system to reach the blood or the bloodstream directly. These cancer cells eventually reach the brain tissue through the bloodstream where they develop into tumors. Metastatic brain tumors are the most common type of tumor found in the brain and are much more common than primary brain tumors. Metastatic tumors are usually named after the type of tissue from which the original cancer cells arose (for example, metastatic lung or metastatic breast cancer). Brain blood flow usually determines where the metastatic cancer cells will lodge in the brain; about 85% locate in the cerebrum (the largest portion of the brain, located in the upper part of the skull cavity). But in fact , the majority of metastatic brain tumors occur at more than one site in the brain tissue.