 Individuals differ in their inherited tendency to develop cancer , and cancer is a genetic disease . The process of cancer development in the body is a combination of events . Mutations occasionally occur within cells in the body as they divide . Although these mutations will not be inherited by any offspring , they can affect the behavior of cells , sometimes causing them to grow and divide more frequently . There are biological mechanisms that attempt to stop this process ; signals are given to inappropriately dividing cells that should trigger cell death , but sometimes additional mutations occur that cause cells to ignore these messages . An internal process of natural selection occurs within the body and eventually mutations accumulate within cells to promote their own growth , creating a cancerous tumor that grows and invades various tissues of the body . 
