How cancer spreads
Cancer cells often travel to other parts of the body where they begin to grow and form new tumors. This happens when the cancer cells get into the body’s bloodstream or lymph vessels. Over time, the tumors replace normal tissue. The process of cancer spreading is called metastasis.
How cancers differ
No matter where a cancer may spread, it’s always named for the place where it started. For example, breast cancer that has spread to the liver is called metastatic breast cancer, not liver cancer. Likewise, prostate cancer that has spread to the bone is called metastatic prostate cancer, not bone cancer.
Different types of cancer can behave very differently. For instance, lung cancer and skin cancer are very different diseases. They grow at different rates and respond to different treatments. This is why people with cancer need treatment that is aimed at their kind of cancer.
Tumors that are not cancer
Not all tumors are cancer. Tumors that aren’t cancer are called benign. Benign tumors can cause problems – they can grow very large and press on healthy organs and tissues. But they cannot grow into (invade) other tissues. Because they can’t invade, they also can’t spread to other parts of the body (metastasize). These tumors are almost never life threatening.
How common is cancer?
Half of all men and one-third of all women in the US will develop cancer during their lifetimes.
Today, millions of people are living with cancer or have had cancer. The risk of developing many types of cancer can be reduced by changes in a person’s lifestyle, for example, by staying away from tobacco, limiting time in the sun, being physically active, and healthy eating.
There are also screening tests that can be done for some types of cancers so they can be found as early as possible – while they are small and before they have spread. In general, the earlier a cancer is found and treated, the better the chances are for living for many years.