I. is a group of diseases characterized by an uncontrolled growth of abnormal cells. If the spread of these abnormal cells is not controlled, can cause death. Most s take the form of tumors, although not all tumors are s. A tumor is simply a mass of new tissue that serves no physiological purpose. It can be benign, like a wart, or malignant, like cancer. Benign tumors are made up of cells similar to the surrounding normal cells and are enclosed in a membrane that prevents them from penetrating neighboring tissues. They are dangerous on ....