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:
“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)
“Ever since I was a kid my folks fed me bigotry for breakfast and ignorance for supper. Never, not once did they ever make me feel proud of where I was born. Thats it. That was a cancer they put in me. No knowledge of my country. No pride. Just a hymn of hate.”
—Samuel Fuller (b. 1911)
“I wish more and more that health were studied half as much as disease is. Why, with all the endowment of research against cancer is no study made of those who are free from cancer? Why not inquire what foods they eat, what habits of body and mind they cultivate? And why never study animals in health and natural surroundings? why always sickened and in an environment of strangeness and artificiality?”
—Sarah N. Cleghorn (19761959)