The thought crosses everyone's mind at some time or other.
Cancer is defined as abnormal cells with uncontrolled cell growth.
It basically takes over the body one cell at a time. The ironic thing is that, often, cancer is curable, especially if detected at an early stage. Tumors develop when abnormal cells start to grow out of control. Tumors may be close enough to the skin to feel them, but not always. Cancer is not completely understood even in today's medical technology.