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.
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. Prevention, Avoiding smoking or quitting smoking if you do smoke is one of the best ways to prevent cancer. Many cancers can be prevented by avoiding other risk factors such as excessive exposure to sunlight and heavy drinking. In addition, some cancers can be prevented by eating a healthy diet which is low in fat and high in fiber.
Symptoms of cancer depend on the type and location of the tumor. For example, lung cancer can cause coughing, shortness of breath or chest pain while cancer of the colon often causes weight loss, diarrhea, constipation and blood in the stool. Some cancers may not have any symptoms at all. Treatment also varies based on the type of cancer and its stage. The stage of a cancer refers to whether or not the tumor has spread from its original location. If the cancer is confined to one location and has not spread, the goal for treatment would be surgery and cure.