Cancer is a deadly disease that causes cells to grow out of control. It can grow into tissue that surrounds organs and other parts of the body, forming tumors. Cancer can also spread to other areas of the body through blood or lymphatic systems. In the United States, cancer is the second leading cause of death, after heart disease. But it’s treatable if diagnosed early. And researchers are constantly improving treatments, with the goal of curing more and more types of cancer.
Almost everyone knows someone who has had cancer, or who has died of the disease. But many people do not understand how cancer works or why it develops. Scientists have many ideas about what causes cancer, and some are related to genes or the environment. Many of these factors are uncontrollable, and they may be passed down from one generation to the next.
Researchers have learned that cancer begins in cells, which are the basic building blocks of tissues. Cells make proteins that help the body grow and repair itself. They also divide to form new cells as the body needs them. Normally, when old or damaged cells aren’t needed, they die and are replaced by new cells. Cancer develops when the process of making and dividing cells goes wrong.
Scientists have discovered that the genes inside a cancer cell often have changes (mutations). Mutations change the instructions that tell the cell when to grow and divide. Cancers with more mutations have a greater chance of growing and spreading to other parts of the body.
Another reason cancer is deadly is that it can invade and destroy healthy tissue. For example, cancer that grows into a blood vessel and then into a bone can kill the person. The most common cancers start in the lungs, breasts, prostate, and colorectal tract. Some cancers develop in the bones, muscles, and skin, and others begin in the lymph nodes, liver, or brain.
Some types of cancer are easier to cure than others. Doctors know how to detect and treat most of them. They also have developed systems for classifying cancers based on how they grow and spread. Knowing how cancers grow and spread can help doctors plan treatment and give patients better information about their prognoses.