Cancer Causes

Cancer is a group of more than 100 different diseases. Cancer occurs when cells become abnormal and keep dividing and forming more cells without control or order. All organs of the body are made up of cells. Normally, cells divide to produce more cells only when the body needs them. This orderly process helps keep us healthy. If cells keep dividing when new cells are not needed, a mass of tissue forms. This mass of extra tissue, called a growth or tumor, can be benign or malignant.

Malignant tumors are cancer. Cancer cells can invade and damage nearby tissues and organs. Also, cancer cells can break away from a malignant tumor and enter the bloodstream or the lymphatic system. This is how cancer spreads from the original (primary) tumor to form new tumors in other parts of the body. The spread of cancer is called metastasis.

Most cancers are named for the type of cell or the organ in which they begin. When cancer spreads, the new tumor has the same kind of abnormal cells and the same name as the primary tumor. For example, if lung cancer spreads to the liver, the cancer cells in the liver are lung cancer cells. The disease is called metastatic lung cancer (not liver cancer).

Our current understanding of the causes of cancer is incomplete, but it is clear that cancer is not caused by an injury, such as a bump or bruise. And although being infected with certain viruses may increase the risk of some types of cancer, cancer is not contagious. No one can "catch" cancer from another person.

Cancer develops gradually as a result of a complex mix of factors related to environment, lifestyle, and heredity. Scientists have identified many risk factors that increase the chance of getting cancer. They estimate that about 80 percent of all cancers are related to the use of tobacco products, to what we eat and drink, or, to a lesser extent, to exposure to radiation or cancer-causing agents (carcinogens) in the environment and the workplace. Some people are more sensitive than others to factors that can cause cancer.

Many risk factors can be avoided. Others, such as inherited risk factors, are unavoidable. It is helpful to be aware of them, but it is also important to keep in mind that not everyone with a particular risk factor for cancer actually develops the disease. In fact, most do not. People at risk can help protect themselves by avoiding risk factors where possible and by getting regular checkups, so that if cancer develops, it is likely to be found early.

Below are some of the factors that are known to increase the risk of cancer:

1. Tobacco
2. Diet
3. Sunlight
4. Alcohol
5. Radiation
6. Chemicals and Other Substances
7. Hormone Replacement Therapy
8. Diethylstilbestrol (DES)