Cancer

Cancer is a disease in which some of the body's cells grow out of control. Your body is made of trillions of tiny cells. Normally, cells follow strict rules. They grow, do their job, and die when they are supposed to. In cancer, something goes wrong with those rules. The bad cells keep making more of themselves and crowd out the healthy ones.

Cancer starts in the DNA inside a cell. DNA is the set of instructions that tells the cell how to act. When the DNA gets damaged, the cell can forget when to stop dividing. One bad cell becomes two, then four, then thousands. Over time, this clump of cells can form a lump called a tumor.

Not every tumor is cancer. Some tumors stay in one place and do not spread. Those are called benign. Cancer tumors are different because they can break off and travel through the blood to other parts of the body. This spreading is called metastasis. It is what makes cancer so dangerous.

There are more than 100 kinds of cancer. They are usually named for where they start. Lung cancer starts in the lungs. Skin cancer starts in the skin. Leukemia starts in blood cells. Each kind acts a little differently and needs different treatment.

What makes a cell go bad in the first place? Sometimes the answer is clear. Smoking damages lung cells. Too much sunlight can damage skin cells. Some viruses can also cause cancer. But sometimes cancer just happens by chance, even to people who did everything right. That is one reason it feels so unfair.

Doctors fight cancer in three main ways. Surgery cuts the tumor out. Radiation uses strong invisible rays to kill cancer cells. Chemotherapy uses powerful medicines that travel through the whole body. Newer treatments train the patient's own immune system to attack the cancer. This is called immunotherapy, and it has saved many lives that could not have been saved 20 years ago.

Cancer has been around for a long time. Scientists have even found signs of it in ancient Egyptian mummies. About one in three people will get some form of cancer in their lifetime. The good news is that survival rates keep going up. In the 1970s, about half of cancer patients in the United States lived more than five years after diagnosis. Today, nearly seven out of ten do.