Normal cells grow, divide and produce more cells of the same kind that will serve the same function; ultimately, they die off. Occasionally however, cells divide and grow rapidly; the mass that forms as a result is called a tumor. When this tumor continues to grow and spread, it is known as cancer.
Malignant vs. Benign
Not all tumors are malignant; benign tumors can be removed surgically, and are non-recurring and non life-threatening. Malignant cells however grow in an uncontrolled manner, spreading to adjacent tissues. Some of these outlaw cells break away and travel through the bloodstream and/or lymphatic system and establish themselves in distant parts of the body. This process is called metastasis; the new cancers in these other parts of the body are called secondary.
Ironically, cancer represents a form of immortality. Were it not for the fact that cancer ultimately kills its host by interfering with the function of vital organs, these cells would live forever. Depending on the type of cancer, it may take many years before symptoms become manifest.
Cancer is caused by exposure to substances called carcinogens. The most common is tobacco; cigarettes have long been known to cause lung cancer in addition to emphysema and other respiratory ailments; however, "smokeless" tobacco can cause cancer of the mouth and jaw as well. People can also develop cancer from exposure to "second-hand smoke" by living and working around those who use tobacco. Alcohol consumption combined with tobacco use can greatly exacerbate the chances of developing cancer, particularly of the throat.
Another well-known carcinogen is asbestos, which when combined with tobacco use, can raise the chances of developing mesothelioma lung cancer by as much as 9000%. Asbestos exposure is also the sole known cause of mesothelioma, a rare but deadly cancer of the visceral linings including the pleura (pleural mesothelioma), peritoneum (peritoneal mesothelioma) and pericardium (pericardial mesothelioma). Other carcinogens include any number of industrial chemicals from aluminum plants, chemical plants and oil refineries that now permeate the environment as well as nuclear radiation from power plants.
It is not fully known how a cell mutates and becomes malignant, nor why some people with excellent health develop cancer readily while others may smoke heavily for years and never get the disease. Research indicates that some people are genetically predisposed to cancer.
It is also known that certain substances interact with cells in DNA in some way that causes the mechanism responsible for apoptosis ("cell death") to stop functioning. In the case of malignant mesothelioma, a recent European study implicated chronic inflammation caused by the presence of asbestos fibers.
Treatment and Cures
At present, there are no known cures for cancer other than prevention. Cancer goes through four stages (see mesothelioma stages), starting from a relatively small, localized tumor and ending with the cancer spreading throughout the body. If diagnosed in its earliest stages, cancerous tissue can be removed surgically or treated with chemicals or radiation. Attempts to treat cancer with immunotherapy has had some limited success, but has largely been stymied by the fact that antibodies fail to recognize cancer as a pathogenic invader. However, chemotherapy drugs are able to have some effect by interrupting the cancer cells' reproductive cycles.
By the time most cancers have reached the final stages, the only realistic treatment options are palliative ones that can at best make the patient's final weeks or months more comfortable.
More on Other Types of Cancer
Find out more about how breast cancer develops, who is at risk, new treatments, and possible asbestos risk.
Learn more about colon cancer (also known as colorectal cancer), including risk factors, treatment, smoking and asbestos exposure hazards.
Leukemia, a cancer of the blood and bone marrow, is actually the name of several different blood and marrow cancers and is more common in children. New studies suggests there may be growing evidence connecting asbestos exposure to the development of leukemia.
While the connection between smoking and lung cancer is widely publicized, there are others at risk, as well, including those exposed to diesel fumes, radon, and asbestos.
Find out more about melanoma, a cancer which affects the skin. Learn who's at risk and what you can do to prevent skin cancers.
Ovarian cancer affects the women's reproductive organ and develops within the ovaries. Studies now indicate that external risk factors, including exposure to asbestos, may directly affect a woman's susceptibility to the development of ovarian cancers.
Find out more about cancer of the pancreas. risk factors for the development of pancreatic cancer include smoking, as well as chronic conditions like diabetes.
Australian and Finnish studies have now implicated asbestos in the development of prostate cancer, a malignancy that develops in the male reproductive organ.
Kidney cancer affects the blood filtration system in the body. Most kidney cancers affect the lining of the kidneys and related organs. These are known as "renal cancers."
Dorland's Illustrated Medical Dictionary, 31st ed. (2008).
Thomas, Clayton L., M.D., ed. Taber's Cyclopedic Medical Dictionary. (Philadelphia: F.A. Davis Company, 2000)