A cancer is a type of disease where there are developments of abnormal cells in the body that invade and kill the normal cells and they replicate more and faster without control. It also have the ability to invade other organs or nearby tissue thus affecting the health of the individual. cancer is a type of disease where there are developments of abnormal cells in the body that invade and kill the normal cells and they replicate more and faster without control. It also have the ability to invade other organs or nearby tissue thus affecting the health of the individual.