Cancer is a disease process in which healthy cells have stopped functioning and maturing normally. The normal cycle of cell formation and death is interrupted and the newly mutated (altered) cancer cells begin to multiply uncontrollably, no more functioning as an integral part of the body. Through a process of programmed cell death called apoptosis, normal cells, when formed, mature, live out their life span and die in an orderly manner. On the contrary, cancer cells have lost their capacity to undergo this natural process of cell death. They don't die in an orderly manner, and as they continue to divide and multiply, they eventually form visible tumors.