Background

Definition of Cancer

Cancer is the unregulated multiplication of abnormal cells that can invade the rest of the body through metastasis.

Causes for Cancer

The causes for cancer can be grouped into three main categories: heredity, environment, and lifestyle. Heredity refers to cancer risk factors that can be inherited from your parents, environment refers to risk factors that arise from the place you are in, and lifestyle risk factors come from activities that are part of our daily lives.

Heredity

Chromosomes, the element of the cell which transfers genetic information from parent to daughter cells, are responsible for transmitting the altered behavior of one cancer cell to its progeny. If a chromosome is lost or an extra chromosome is added during mitosis, this will affect the cell and possibly cause cancer. Chronic myeloid leukemia is a cancer where one chromosome 21 is abnormal. Also, if a gene is somehow altered or mutated, it might cause cancer. Examples of this are the BRCA 1 and BRCA 2 genes, mutations of which have been linked to breast and ovary cancer, and can be handed down from parent to child in families.

Environment

It is difficult to tell how much environmental factors affect humans, since cancer-related effects are observed as a result of high doses that either animals or humans received. This means that scientists look at the results of these high doses and try to determine what a low dose would do to a human. It is due to this uncertainty that it is difficult to tell whether or not everyday exposure to suspected substances will be harmful. The American Cancer Society recognizes two environmental sources for cancer in humans. These are certain chemicals and certain types of radiation. Some cancer-linked chemicals are asbestos and chloroform. The types of damaging radiation are ultraviolet (mostly from the sun), and ionizing radiation (for example, radon). The ACS also lists four unproven risks: pesticides, non-ionizing radiation (such as electromagnetic radiation from telephone wires), toxic waste, and nuclear power plants. There are also some rather exotic environmental factors that some people worry may be linked to cancer, such as artificial sweeteners, Agent Orange, and flouridated water.

Lifestyle

How we live our lives and our actions can play a role in our exposure to certain risk factors for cancer. Diet can be an important risk factor for cancer. According to the American Institute for Cancer Research, our diets are directly linked to 30-40% of cancers. They recommend eating more fiber, fruits and vegetables, as well as keeping a healthy weight, to reduce your risk for cancer. Smoking is another big risk factor. Lung cancer is directly related to smoking, as is cancer of the esophagus and several other types of cancer. Lung cancer can also be a result of inhaling secondhand smoke. Alcohol intake has also been linked to cancer. Statistical evidence shows that drinking 3 to 4 glasses of wine per day leads to an increased risk for breast cancer. Liver and rectal cancers have also been related to alcohol consumption.

Types of Cancer

These are the twelve main types of cancer with a short description of each.

Prostate- Cancer of the prostate gland occurs in males, and is more common in older men and African American men. It is the most common type of cancer that men get. Tumor growth obstructs the urethra, which causes it to have the symptoms of bladder obstruction and infection. Tumor cells can then transfer themselves through the bloodstream to the lungs, liver and bones.

Breast - Breast cancer can occur in women of any age. Women who have had a child when they were 35 or younger have a reduced risk for breast cancer than women who either have not had a child, or who had a child after age 35. Women who have a close relative who has breast cancer have a 3.85 times greater chance of getting breast cancer. Breast cancer usually appears as a small, painless mass.

Lung - Lung cancer is the leading type of lethal cancer. Sadly, 80% to 90% of lung cancer could be avoided by not smoking. The risk for lung cancer is greatly increased if two risk factors occur together, such as smoking and asbestos exposure. There are three types of lung cancer: squamous cell cancer, small cell carcinoma, and adenocarcinoma. Squamous cell carcinoma arises from smoking or other pathways, which cause ulcers and infections in the lining of the lung. Small cell carcinoma is located in hormone-producing cells, can metastatize to other parts of the body easily, and tend to produce excess amounts of hormones like seratonin. Adenocarcinoma of the lung is unusual, it occurs around the outer edge of the lungs, and is dangerous because it is hard to diagnose it early.

Colorectal - It is not understood why the large intestine has a much higher incidence of cancer than the small intestine, even though it is much shorter. Diet, heredity, and location of residence have been shown to play a part in the incidence of colorectal cancer. In men, the cancer is generally located in the sigmoid colon, and causes bowel obstruction. In women, the cancer appears in the ascending colon, and ulcers result.

Bladder - Bladder cancer is generally the result of smoking (from chemicals present in cigarettes), exposure to other chemicals, or an infection by a parasitic worm. Men are more likely to have this cancer than women, and it is usually found in older people. This type of cancer does not tend to metastatize.

Non-Hodgkin's Lymphoma - Lymphoma is cancer that occurs in the lymph nodes, the organs which house the white cells for the immune response. Hodgkin's disease is different on a cellular level from non-Hodgkin's lymphoma, and it is not so widespread through the body. People of any age can develop this type of cancer, with the risk for it increasing until about age 80. Non-Hodgkin's lymphoma is caused by high doses of radiation, using immunosuppressive drugs while contracting an infection with the Epstein-Barr Virus, and people infected with AIDS tend to develop this type of virus.

Uterine - Uterine cancer is the most common of the cancers found in the female reproductive system. It is usually curable because it is found early. The hormone estrogen is the cause for this type of cancer, and this is the reason why women on estrogen therapy after menopause have a higher risk for it unless they take progesterone as well. This cancer is not hereditary.

Melanoma of the Skin - Malignant melanoma occurs on the skin, particularly in areas that receive a good deal of exposure to the sun. Moles and beauty marks account for a third of all tumor locations. However, these tumors can form anywhere there is pigment, such as the eye. Melanoma can be cured 100% if it is found before it has begun to metastatize.

Kidney - The kidney's function is to clean the blood of waste products so they can be excreted. The most common type of kidney cancer is renal cell carcinoma. Smoking, asbestos and cadmium exposure all increase the risk of developing this cancer.

Leukemia - Leukemia affects the blood-producing cells in bone marrow, and can eventually affect the spleen and liver. In late stages, leukemia can affect all organs. Patients with this disease have a hard time fighting off infections, cannot stop bleeding from capillaries, and eventually develop anemia as their blood cells disappear and are replaced by leukemia cells.

Ovarian - The ovaries are responsible for producing many female hormones. The causes for ovarian cancer have not been determined. Certain risk factors can affect your chances of getting it, such as having a close family member with it, or taking certain fertility drugs.

Pancreatic - The pancreas produces digestive enzymes in its exocrine part, and digestive hormones in the endocrine part. The exocrine part is where most pancreatic cancers occur. They are the result of the use of tobacco products and exposure to certain chemicals. Pancreatic cancer has a low survival rate.