Cancer is a growth of abnormal cells in the body.
These cells have lost the normal signals that regulate cell growth. They have the ability to invade surrounding tissues or spread to other parts of the body. Cancers can start in almost any part of the body, but the most common area is in the cells lining the major organs. The lining or skin of the colon and lungs, the lining of the ducts in the prostate or breast, or the skin on the outside of the body are common areas for cancers to develop. A cell must undergo a number of changes in order to become a malignant cancer cell.