In general, cancer appears to be caused by abnormal regulation of cell growth. Typically, the growth of cells in the body is strictly controlled -- new cells are made as needed to replace older ones or to perform needed functions. If the balance of cell growth and death is disturbed, cancer may occur.
Problems in the regulation of cell growth can be caused by abnormalities of the immune system, which normally would detect and stop aberrant growth. Other potential causes of cancer include radiation, sunlight, tobacco, certain viruses, benzene, certain poisonous mushrooms, and aflatoxins amongst many others.
The three most common cancers in men are prostate cancer, colon cancer and lung cancer. While in women, the three most frequently occurring cancers are breast cancer, colon cancer and lung cancer. Certain cancers are more common in particular geographic regions. For example in Japan, there are many cases of gastric (stomach) cancer while in the U.S. this type of cancer is relatively rare. Dietary differences may account for the variance.
Another tumor that is much more prevalent in other parts of the world compared with the U.S. is liver cancer. This cancer is often caused by viral infections with Hepatitis B and C, and is also linked with exposure to aflatoxins, which can be found in certain contaminated foods.
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