What is Cancer?
Cancer develops when cells in a part of the body begin to grow out of control. Although there are many kinds of cancers, all begin because of out-of-control growth of abnormal cells.
Normal body cells grow, divide, and die in an orderly fashion. During the early years of a person’s life, normal cells divide more rapidly until the person becomes an adult. After that, cells in most parts of the body divide only to replace worn-out or dying cells and to repair injuries.
Because cancer cells continue to grow and divide, hey are different from normal cells. Instead of dying, they outlive normal cells and continue to form abnormal cells.
Cancer cells often travel to other parts of the body, where they begin to grow and replace normal tissue. This process, called metastasis, occurs as the cancer cells get into the bloodstream or lymph vessels of our body. When cells from a cancer like breast cancer spread to another organ like the liver, the cancer is still called breast cancer, not liver cancer.
Cancer cells develop because of damage to their DNA. DNA is in every cell and directs all its activities. Most of the time when DNA becomes damaged the cell is able to repair it. In cancer cells, the damaged DNA is not repaired.
People can inherit damaged DNA, which accounts for inherited cancers. Many times though, a person’s DNA becomes damaged by exposure to something in the environment, like smoking.
Most people think of cancer as a solid tumor. But some cancers, like leukemia, do not form tumors. Instead, these cancer cells involve the blood and blood-forming organs, and circulate through other tissues where they grow.
Remember that not all tumors are cancerous. Benign (noncancerous) tumors do not spread to other parts of the body (metastasize) and, with very rare exceptions, are not life threatening.
Different types of cancer behave very differently. For example, lung cancer and breast cancer are very different diseases. They grow at different rates and respond to different treatments. That is why people with cancer need treatment that is aimed at their particular type of cancer.
Cancer is the second leading cause of death in the United States. Half of all men and one-third of all women in the U.S. will develop cancer during their lifetimes. Today, millions of people are living with caner or have had cancer. The risk of developing most types of adult cancers can be reduced by changes in a person’s lifestyle, for example, by quitting smoking, reducing sun exposure, and eating a healthier diet. Generally, the sooner a cancer is found and treatment begins, the better are the chances for living for many years.