What Is Cancer?

Ages 3-5 Simple Explanation

You know how your body is made up of teeny-tiny building blocks called cells? They're so small you can't see them, but they're everywhere — in your skin, your bones, your tummy, everywhere! Cells are like tiny workers that keep your body running.

Usually, your cells follow rules. They grow, they do their job, and when they get old, new cells take their place. But sometimes, some cells stop following the rules. They start growing too fast and making too many copies of themselves. When that happens, it's called cancer.

When someone in your family has cancer, it means doctors found some of those rule-breaking cells in their body. The doctors are going to work really hard to get rid of those bad cells. The person might need to take strong medicine or visit the doctor a lot.

Having cancer doesn't mean someone did anything wrong, and you can't catch cancer from someone like you catch a cold. The person with cancer still loves you just the same. It's okay to feel sad or worried, and it's always okay to ask questions and give lots of hugs.

Ages 6-8 More Detail

Your body is made of trillions of tiny cells, and normally those cells know exactly what to do. They grow, they divide to make new cells, and old cells die to make room. It's all very organized, like a well-run classroom where everyone follows the rules.

Cancer happens when some cells stop following the rules. Instead of growing and dividing in an orderly way, these cells start multiplying out of control. They make copies of themselves even when the body doesn't need them. These extra cells can pile up and form a lump called a tumor.

Not all tumors are cancer. Some lumps are harmless and just sit there. But cancer cells are the kind that can keep growing and sometimes spread to other parts of the body. That's what makes cancer serious and why doctors need to treat it.

Doctors have several ways to treat cancer. Sometimes they do surgery to remove the bad cells. Sometimes they give strong medicine called chemotherapy that kills the fast-growing cancer cells. Sometimes they use special beams of energy called radiation to shrink the cancer. Many people use a mix of these treatments.

If someone in your family has cancer, it's normal to feel scared, sad, or confused. Cancer is not something you can catch from another person — it's not like a cold or the flu. The person with cancer didn't do anything to cause it. The most important thing you can do is keep being yourself, keep asking questions when you have them, and know that doctors are doing everything they can to help.

Ages 9-12 Full Explanation

Your body is made up of trillions of cells that are constantly growing, dividing, and dying in a very organized cycle. Old or damaged cells die off, and new cells are created to replace them. This process is tightly controlled — your body has built-in instructions that tell cells when to grow, when to divide, and when to stop. Cancer happens when those instructions get messed up in certain cells.

When a cell's instructions are damaged, it can start dividing when it shouldn't and refuse to die when it's supposed to. These out-of-control cells pile up and can form a mass called a tumor. Some cancers form solid tumors in organs or tissues, while others, like leukemia, affect the blood and don't form lumps. What makes cancer especially tricky is that cancer cells can sometimes break away and travel to other parts of the body through the blood, spreading the disease.

Cancer is not just one disease — there are actually over 100 different types, named after where they start in the body. Lung cancer starts in the lungs, skin cancer starts in the skin, and so on. Some cancers grow fast and some grow slowly. Some are easier to treat than others. That's why when someone gets diagnosed with cancer, the doctors spend time figuring out exactly what kind it is before deciding on the best treatment plan.

Treatment depends on the type and stage of cancer. Surgery removes the cancer if it's in one spot. Chemotherapy uses powerful medicine that travels through the whole body to kill cancer cells wherever they are — but it can also make the person feel pretty sick because it affects healthy cells too. Radiation therapy uses focused beams of energy aimed right at the cancer to destroy it. Newer treatments like immunotherapy help the body's own defense system recognize and fight cancer cells.

If someone you love has been diagnosed with cancer, it's totally normal to feel scared, angry, sad, or even guilty — all of those feelings are okay. Cancer is not contagious, so you can't catch it by being near someone who has it. The person didn't get cancer because of anything they did wrong, and it's definitely not your fault. The best thing you can do is be there for them, ask questions when you're confused, and talk to an adult you trust about how you're feeling. Many people who get cancer do recover, and treatments are getting better all the time.