Cancers have a tendency to spread to other tissues and organs. For example, a cancer that develops in the lung, can spread to the bones or to the brain . This process is called Metastasis , and normally takes place in most cancer. Cancer cells have very complex abilities, one of which is their ability to find their ways to blood stream. Once in blood stream, they can travel to almost every part of the body.
Cancer is a very common problem in the world.
In United States, it is the second leading cause of death after heart disease and it afflicts more than 1.3 million people every year. Cancer is slightly more frequent in men than women.