This year, over 500,000 Americans are expected to die of cancer. Let's take a closer look at the diseases effects on the body. The term "cancer" refers to a group of diseases, which stem from mutations in the body's cells. As the abnormal cells grow and spread, cancer can lead to physical symptoms and, in one of four people, death. Generally, cancer harms a patient in two ways - by physically blocking or pressing on the body's organs, and by reproducing instead of normal, healthy cells. Of course, every type of cancer is different and leads to a specific set of symptoms and possible consequences. Usually though, symptoms begin locally, at the original site of cell mutation. A person experiencing local cancer symptoms may notice an unusual lump, ulcer, sore, or swelling, which is often due to tumor formation. Bleeding or pain may also accompany the growth. As cancer spreads, other symptoms occur. Because many cancers form in or spread to the lymph nodes, swelling in this area is very common. Lymph node swelling may be noticed on either side of the neck, in the armpits, around the groin, behind the ears, and on the back of the neck. In addition, unexplained fatigue, fever, or severe weight loss may be signs of cancer, as the disease uses up much of the body's energy supply. The possible effects of cancer are even harder to determine, because every type is distinct and every person responds to treatment in a different way. When cancer has not yet spread beyond a single tumor, it can still cause pain and illness by pressing against nerves or blocking nearby organs. For example, the presence of a cancerous tumor in the lungs could grow in the airway, obstructing oxygen flow in the body. Once cancer begins metastasis, or the process of spreading, even more serious problems can result. Since cancer cells reproduce at a much faster rate than healthy cells, they can displace, or essentially take over for healthy cells in certain areas. This is what happens in patients with leukemia, a type of cancer that begins in the bone marrow, where blood cells are produced. In a healthy person, the bone marrow makes three types of blood cells: white blood cells - which fight infection, red blood cells - which carry oxygen to body tissues, and platelets - which help form clots to control bleeding. People with leukemia begin to make too many white blood cells and stop making enough equally vital red blood cells and platelets. Unfortunately, no matter how exactly it happens, untreated cancer can eventually overrun healthy cells in vital parts of the body thereby leading to death. The good news is that modern medical screening and treatment options have raised the cancer survival rate higher than ever. If you or someone you love has been diagnosed with cancer, talk to your doctor about what to expect and the treatment options that may be right for you. Want to learn more? Check out other videos and sources on this site for more information.