What Is Cancer?
The body is made up of hundreds of millions of living cells. Normal body cells grow, divide, and die in an orderly way.
- Cells divide in young people to help them grow. Cells divide in adults primarily to replace worn-out, damaged, or dying cells.
- There are many kinds of cancer. They all start when cells start to grow out of control.
- Cancer cell growth is different from normal cell growth. Instead of dying, cancer cells keep on growing and form new cancer cells. These cancer cells can grow into (invade) other tissues, something that normal cells cannot do. Being able to grow out of control and invade other tissues are what makes a cell a cancer cell.
- Generally, cancer cells form a tumor. Some cancers, such as leukemia, rarely form tumors. Instead, these cancer cells are in the blood and blood-forming organs.
- When cancer cells get into the bloodstream or lymph vessels, they can travel to other parts of the body. There they begin to grow and form new tumors that replace normal tissue. This process is called metastasis(muh-tas-tuh-sis).
- No matter where a cancer may spread, it is always named for the place where it started. For instance, breast cancer that has spread to the liver is still called breast cancer, not liver cancer.
- Different types of cancer can behave very differently.
- Different types of cancer grow at different rates and respond to different treatments.
- This is why people need treatment that is aimed at their own kind of cancer.
NOTE: Not all tumors are cancer. Tumors that are not cancer are called benign(be-nine).
- Benign tumors cannot grow into other tissues. Because of this, they also can't spread to other parts of the body (metastasize). These tumors are almost never life threatening.
- Still, benign tumors can cause other problems. For instance, they can grow very large and press on healthy organs and tissues.
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