Aging & Health A to Z
Basic Facts & Information
What is Cancer?
When cells grow normally in your body, they divide into exact copies of themselves. When there are enough cells needed for a particular part of the body, the cells stop multiplying.
But sometimes cells grow abnormally. Often, this isn’t dangerous, and the cells grow into a clump of cells known as a benign tumor (much like a wart). These benign tumors grow slowly. Often they can be easily removed surgically, or simply ignored.
But at other times, cells start to grow in a completely “out-of-control” way, invading other parts of the body. This type of abnormal cell growth is called cancer. Many cancer cells together form a clump or mass called a malignant tumor. Other cancers, such as leukemia —a cancer of the bone marrow and blood—do not form tumors. Cancer can spread from its original location to another part of the body. This is called metastatic cancer.
Although our bodies have ways of detecting and repairing abnormal cells, these processes often don’t work as well when we get older. Our immune systems, which normally destroy old, damaged, or abnormal cells, are also less effective as we age. For these reasons, cancer is primarily a disease of older adults. In the US, half of all cancers occur in people over the age of 65.
The medical study of cancer and its treatment is called oncology. Physicians who specialize in cancer are known as oncologists.
How Common is Cancer?
Half of all men and one-third of all women in the US will be diagnosed with cancer sometime during their lifetimes. After heart disease, it is the leading cause of death in the US. The most common cancers are lung cancer, colon cancer, breast cancer (for women), and prostate cancer (for men).
In the last few years, there has been a decline in cancer deaths for both men and women. The overall rate of new cancer diagnoses has also decreased annually. This promising sign is due to improvements in cancer prevention, detection, and treatment.
Updated: March 2012
Posted: March 2012