A cancer is an abnormal growth of cells (usually derived from a single abnormal cell). The cells have lost normal control mechanisms and thus are able to multiply continuously, invade nearby tissues, migrate to distant parts of the body, and promote the growth of new blood vessels from which the cells derive nutrients. Cancerous (malignant) cells can develop from any tissue within the body.
Although there are many different types of cancer, which have different causes and risk factors, doctors estimate that about 40% of cancers are preventable. Also, individual people have different risks for developing different cancers. Therefore, no set of prevention strategies is effective in every person. However, some general strategies do reduce the risk of cancer or cancer complications in many people. These general strategies fall into 3 categories: