Cancer i/ˈkænsər/, known medically as a malignant neoplasm, is a broad group of various diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the body through the lymphatic system or bloodstream. Not all tumors are cancerous. Benign tumors do not grow uncontrollably, do not invade neighboring tissues, and do not spread throughout the body. There are over 200 different known cancers that afflict humans.
Determining what causes cancer is complex. Many things are known to increase the risk of cancer, including tobacco use, certain infections, radiation, lack of physical activity, obesity, and environmental pollutants. These can directly damage genes or combine with existing genetic faults within cells to cause the disease. Approximately five to ten percent of cancers are entirely hereditary.
Cancer can be detected in a number of ways, including the presence of certain signs and symptoms, screening tests, or medical imaging. Once a possible cancer is detected it is diagnosed by microscopic examination of a tissue sample. Cancer is usually treated with chemotherapy, radiation therapy and surgery. The chances of surviving the disease vary greatly by the type and location of the cancer and the extent of disease at the start of treatment. While cancer can affect people of all ages, and a few types of cancer are more common in children, the risk of developing cancer generally increases with age. In 2007, cancer caused about 13% of all human deaths worldwide (7.9 million). Rates are rising as more people live to an old age and as mass lifestyle changes occur in the developing world.
Famous quotes containing the word cancer:
“The same people who tell us that smoking doesnt cause cancer are now telling us that advertising cigarettes doesnt cause smoking.”
—Ellen Goodman (b. 1941)
“Madness is locked beneath. It goes into tissues, is swallowed by the cells. The cells go mad. Cancer is their flag. Cancer is the growth of madness denied.”
—Norman Mailer (b. 1923)
“We need cancer because, by the very fact of its incurability, it makes all other diseases, however virulent, not cancer.”
—Gilbert Adair, British author, critic. Under the Sign of Cancer, Myths and Memories (1986)