Cells go through a life cycle in which there is normally a balance between cellular growth and death. Cancer results when cells grow and divide uncontrollably. Most of a normal cell's life is spent in growth, DNA replication and normal cell functions, something that is referred to as interphase. Only about 10% of the time is a normal cell involved in division, or mitosis.
Mitosis is necessary for tissue repair, but cancer cells grow and reproduce more quickly than is necessary to maintain a healthy balance of growth, division and death of cells. They grow so much, and so uninhibited by normal regulatory processes that a tumor or mass of abnormal cancer cells develops.
Cancer develops due to genetic predisposition and exposure to cancer-causing substances which cause genetic mutation. These mutations in turn are responsible for unmitigated cell growth and division. Unchecked and uninhibited, cancer cells proceed through the phases of a cell cycle more quickly than normal. They divide and produce more cancer cells which develop into a tumor. This unmediated accelerated growth and reproduction, or mitosis, normally the shortest phase of the cell cycle, is what characterizes cancer cells.
