When cells in a part of the body begin to grow out of control the result is cancer. Normally, after a person reaches adulthood, cells grow and divide only to replace worn out or dying cells. Cancer cells, however, grow and divide not as replacements but because of damaged DNA. The DNA can be inherited in the damaged state or can be the result of external factors such as smoking or radiation.

Metastasis occurs when cancer travels to other parts of the body through the blood stream. There are many types of cancer that behave in many different ways and all have the potential to be deadly. In fact, thousands of deadly cancer cells are produced within our bodies every day as a byproduct of living. This is normally not a problem for healthy immune systems, which destroy the cancer cells on contact. However if our immune system has been compromised, any of the cells have the potential to divide and eventually conquer.