Under normal circumstances, when a cell's DNA changes, the body fixes the DNA. In a cancer cell, however, the body cannot fix the DNA, which then leads to the affected cell's daughter cells carrying the same "bad" DNA.
For the most part, the cancer cells form tumors, sort of like a control station. If the tumor is not removed quickly enough, cells may break off the tumor and enter the bloodstream, traveling to other parts of the body. This is called metastasis. At this stage, the cancer is very hard to completly remove.
Frighteningly, cancer is the second largest cause of all deaths in the United States. Based on current statistics, roughly 50 percent of all men will be infected by cancer at one point or another in their lifetime. A third of all the women in the U.S. will also have cancer.
