The term neoplasm refers to an abnormal growth of tissue caused by the rapid division of cells that have undergone some form of mutation. The body is made up of trillions of cells that grow, divide, and die in an orderly fashion. This process is a tightly regulated one that is controlled by the DNA machinery within the cell. When a person is growing up, the cells of the body rapidly divide, but once adulthood is reached, cells generally only divide to replace worn-out, dying cells or to repair injured cells.