Some cancers are easily cured, others are more difficult to treat. This depends largely on the place in the body where the cancer cells grow, how large the tumor is when it is first found, and if it has spread. Generally, each type of cancer has its own symptoms, outlook for cure, and methods of treatment. No one knows for sure why a normal cell becomes a cancer cell. Many causes of cancer have been identified.
Scientists agree that people can get cancer through repeated long-term contact with carcinogens .
These include tobacco, sunlight, X-rays, and certain chemicals that may be found in the air, water, food, drugs and workplace. Our personal habits and lifestyle may contribute to most cancers. Cancers develop slowly in people. They usually appear five to 40 years after exposure to a carcinogen. For example, cancer of the lung may not occur until 30 years after a person starts smoking.