Cancer is the uncontrolled growth of cells. This abnormal growth is the result of mutations in the genetic material of the cells, either spontaneous or brought on by environmental factors such as ultraviolet radiation or asbestos. This growth leads to a collection of mutated cells called a tumor. The tumor can be benign, meaning that it is comparatively harmless and restricted to one type of tissue. Alternately, it can be malignant, which means it can grow into surrounding tissue or migrate to different parts of the body. When a malignant tumor spreads to other tissues, this is known as metastasis.

Cell Replication

Normally, animal cells grow with a variety of checkpoints. For example, when a person cuts her finger, skin cells will divide and grow to fill the opening, but they will stop growing once the cut is closed. The body has a number of mechanisms to prevent...