A brain tumor is defined as an abnormal growth of cells within the brain or inside the skull. The growth can be benign or malignant. It is further defined as any intracranial tumor created by abnormal and uncontrolled cell division, normally either in the brain itself, in the cranial nerves, in the brain envelopes (meninges), skull, pituitary and pineal gland, or spread from cancers primarily located in other organs (metastatic tumors).
The brain is a soft spongy mass of tissue that is protected by the bones of the skull, three layers of thin tissue (meninges), and a watery fluid that flows through spaces between the meninges and through spaces within the brain. Brain tumors are placed into four grade categories: grade one refers to benign tumors where the cells are like normal brain cells and their growth is slow; grade two means that the tissue is malignant and the cells look less like normal cells than the grade one cells; grade three means the malignant tissues look very different from normal cells and are actively growing; and grade four which means the cells look completely abnormal and the growth is rapid.
Causes of Brain Tumors
Most brain tumors develop from abnormalities of genes involved in cell cycle control, causing uncontrolled cell division. These abnormalities are caused by alterations directly in the genes, or by chromosome rearrangements which change the function of a gene.
There are two types of brain tumors: primary brain tumors that originate in the brain and metastatic (secondary) brain tumors that originate from cancer cells that have migrated from other parts of the body. The National Cancer Institute (NCI) reports that aside from a known association with exposure to vinyl chloride, there are no known chemical or environmental agents that lead to the development of brain tumors.
Vinyl chloride is a carcinogen (a cancer-causing substance). Exposure to vinyl chloride is an environmental risk factor for brain cancer. It is an industrial product used in the production of plastic products such as pipes, wire coatings, furniture, car parts, and housewares; the chemical can also be found in tobacco smoke. Vinyl chloride can be released in the air or water, and it may leak into the environment as a result of improper disposal. People who work in these plants or live in close proximity to them have an increased risk for brain cancer.
There are certain diseases that can lead to brain tumors. These include Multiple endocrine neoplasia type 1 (pituitary adenoma); Neurofibromatosis type 2 which affects the brain and spinal cord; Retinoblastoma a malignant retinal glioma; Tuberous sclerosis (primary brain tumors); and Von Hippel-Lindau disease (retinal tumor, CNS tumors).
Cancer of other Body Parts
Patients with a history of melanoma, lung, breast, colon, or kidney cancer are at risk for secondary brain cancer.
Immune System Disorders
A low or impaired immune system will be more susceptible to the development of lymphomas of the brain or spinal cord. Lymphomas are cancers of lymphocytes, a type of cell of the immune system. Lymphomas usually form in lymph nodes, which are small, bean-sized collections of lymphocytes found throughout the body. Impairment of the immune system may be present at birth or could result from cancer treatments, organ transplant treatments, or from other diseases such as AIDS.
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