Cancer, known medically as a
malignant neoplasm, is a broad group of diseases involving unregulated cell growth. In cancer,
cells divide and grow uncontrollably, forming malignant tumors, and invading 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 invade neighboring tissues and do not spread throughout the
body. There are over 200 different known cancers that affect humans.
[1]
The causes of cancer are diverse, complex, and only partially
understood. Many things are known to increase the risk of cancer,
including
tobacco use,
dietary factors, certain
infections, exposure to
radiation,
lack of physical activity,
obesity, and environmental pollutants.
[2] These factors can directly damage genes or combine with existing genetic faults within cells to cause cancerous mutations.
[3] Approximately 5–10% of cancers can be traced directly to inherited genetic defects.
[4]
Many cancers could be prevented by not smoking, eating more vegetables,
fruits and whole grains, eating less meat and refined carbohydrates,
maintaining a healthy weight, exercising, minimizing sunlight exposure,
and being
vaccinated against some infectious diseases.
[2][5]
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.
[6]
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