As with all medical conditions, there may be many causal factors. Further relevant information on causes of Small Intestine Cancer may be found in:
16 MEDICAL BOOKS ONLINE! Review excerpts from medical books online, free, without registration, for more information about the causes of Small Intestine Cancer.
Researchers have found that cancer develops from mutations within the genes of cells. Thus, cancer is a genetic disease. Cancer susceptibility genes are of two types. Some are oncogenes, which activate cell division and influence embryonic development, and some are tumor suppressor genes, which halt cell division.
These genes are typically found in normal human cells, but certain kinds of mutations may transform the normal cells. Inherited defects may cause a genetic mutation, whereas exposure to a carcinogen may cause an acquired mutation. Current evidence indicates that carcinogenesis results from a complex interaction of carcinogens and accumulated mutations in several genes.
In animal studies of the ability of viruses to transform cells, some human viruses exhibit carcinogenic potential. For example, the Epstein-Barr virus, the cause of infectious mononucleosis, has been linked to Burkitt's lymphoma and nasopharyngeal cancer.
High-frequency radiation, such as ultraviolet and ionizing radiation, damages the genetic material known as deoxyribonucleic acid (DNA), possibly inducing genetically transferable abnormalities. Other factors, such as a person's tissue type and hormonal status, interact to potentiate radiation's carcinogenic effect. Examples of substances that may damage DNA and induce carcinogenesis include:
❑alkylating agents — leukemia
❑aromatic hydrocarbons and benzopyrene (from polluted air) — lung cancer
❑asbestos — mesothelioma of the lung
❑tobacco — cancer of the lung, oral cavity and upper airways, esophagus, pancreas, kidneys, and bladder
❑vinyl chloride — angiosarcoma of the liver.
Diet has also been implicated, especially in the development of GI cancer as a result of a high animal fat diet. Additives composed of nitrates and certain methods of food preparation — particularly charbroiling — are also recognized factors.
The role of hormones in carcinogenesis is still controversial, but it seems that excessive use of some hormones, especially estrogen, produces cancer in animals. Also, the synthetic estrogen diethylstilbestrol causes vaginal cancer in some daughters of women who were treated with it. It's unclear, however, whether changes in human hormonal balance retard or stimulate cancer development.
Some forms of cancer and precancerous lesions result from genetic predisposition either directly (as in Wilms' tumor and retinoblastoma) or indirectly (in association with inherited conditions such as Down syndrome or immunodeficiency diseases). Expressed as autosomal recessive, X-linked, or autosomal dominant disorders, their common characteristics include:
❑early onset of malignant disease
❑increased incidence of bilateral cancer in paired organs (breasts, adrenal glands, kidneys, and eighth cranial nerve [acoustic neuroma])
❑increased incidence of multiple primary malignancies in nonpaired organs
❑abnormal chromosome complement in tumor cells.
Source: Professional Guide to Diseases (Eighth Edition), 2005
Primary tumors of the spinal cord may be extramedullary (occurring outside the spinal cord) or intramedullary (occurring within the cord itself). Extramedullary tumors may be intradural (meningiomas and schwannomas), which account for 60% of all primary malignant spinal cord neoplasms, or extradural (metastatic tumors from breasts, lungs, prostate, leukemia, or lymphomas), which account for 25% of these malignant neoplasms.
Intramedullary tumors, or gliomas (astrocytomas or ependymomas), are comparatively rare, accounting for only about 10%. In children, they're low-grade astrocytomas.
Spinal cord tumors are rare compared with intracranial tumors (ratio of 1:4). They occur equally in men and women, with the exception of meningiomas, which occur mostly in women. Spinal cord tumors can occur anywhere along the length of the cord or its roots.
Source: Professional Guide to Diseases (Eighth Edition), 2005
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