Most people don't usually associate cancer with teens because it's more common in adults. You probably know someone who has had it, such as an older relative or someone in a friend's family.

But teens can get some types of cancer, too. Read on to learn about cancer and how it's treated.

What Is Cancer?

The word cancer actually refers to many diseases, not one. In fact, there are more than 100 types of diseases known collectively as cancer. What they all have in common is the overgrowth of cells, tiny units that make up all living things. Cancer (also known as malignancy, pronounced: muh-LIG-nun-see) occurs when cells begin to grow and multiply in an uncontrolled way.

Normal body cells grow and divide over a period of time until they eventually die. But cancer cells continue to grow and divide and grow and divide. Eventually, they gather to form tumors. Tumors are lumps that can interfere with the body's normal processes. Sometimes cells from a tumor break away and travel to a different tissue or organ. This is called metastasis (pronounced: muh-TASS-tuh-siss).

As scary as all this sounds, most cancers can be treated and controlled and many people with cancer get better and lead normal lives.

How Do People Get Cancer?

No one really knows why cancer grows in certain people. Scientists and researchers are working to discover why some people get cancer and others do not. This will help them to learn whether cancer can be prevented.

Doctors do have some ideas about why people may get cancer, though. The main reasons are genetics and certain environmental or behavioral triggers.

The tendency to develop some types of cancer is believed to be inherited — that is, the genes you were born with might carry a predisposition for cancer. For example, if a close relative has had cancer of the breast or the colon, you may be more likely to inherit the tendency to develop those cancers, even though you may never actually get them.

Some behavioral and environmental triggers can cause changes in the body's cells that push them into a cancerous state. For example, cigarettes are known to increase the risk of lung cancer. Too much exposure to the sun can increase the risk of skin cancer. These types of triggers act on the body slowly over time, so the cancers that may result from them don't show up until a person is an adult. That's one reason why teens don't get the same types of cancers as adults do.

Doctors do know for sure that cancer itself is not contagious, so you don't have to worry about catching it from someone else or spreading it to another person (although people with certain infectious diseases such as AIDS or hepatitis are more vulnerable to certain cancers). Cancer is also never a person's fault. It's simply not true that a person may have done something wrong to get the disease.

How Do People Know They Have Cancer?

The first sign of cancer is a symptom — a signal that something is wrong. There are many different signs that a person may have cancer, just as there are many different forms of the disease. A few of the more common symptoms of cancer include:

• extreme exhaustion
• swelling or lumps in certain parts of the body, such as the abdomen or neck
• headaches
• blurred vision
• nausea
• problems with walking or balance
• more infections
• unusual bleeding

Only you know how your body works and what you feel like when you're healthy. If you haven't been feeling well, it's best to tell an adult who can make sure you see a doctor who will evaluate your symptoms. Cancer, like most illnesses, is easier to treat when it's found early, so when in doubt, check it out.

When cancer is suspected, doctors will order various tests. These might include blood tests, in which blood cells are examined under a microscope for problems, X-rays, or an MRI, a test that can be used to detect tumors.

A doctor who specializes in treating people with cancer is called an oncologist (pronounced: ahn-KOL-uh-jist). They often use a biopsy (pronounced: BYE-op-see) to diagnose cancer. In this procedure, a doctor removes a small tissue sample to examine it for cancer cells.

How Do Doctors Treat Cancer?

Most cancers can be treated, especially the types of cancers teens are likely to get. The number of people who beat cancer goes up every year because of new cancer treatments.

The three common methods for treating cancer are: surgery, chemotherapy, and radiation. Because cancer is different in each patient, each person's treatment plan will be individually designed for him or her. Someone with cancer may undergo any one of these treatments or a combination of them.

Surgery removes cancerous tissue. Depending on the location of the cancer, surgery can be simple or complex, so the operation may be an outpatient procedure (where someone is in and out of the hospital on the same day) or may require that the person stay in the hospital. Generally, the surgeon removes the cancerous tissue along with a small amount of the healthy tissue surrounding it to make sure that all the cancer is removed and has not spread.

The treatment of cancer using medication is called chemotherapy. Certain cancers respond well to chemo, which often can be given on an outpatient basis. Someone who is having chemotherapy may experience nausea, fatigue, hair loss, or other side effects. Some of these side effects happen because chemo medicines may destroy some healthy cells in the process of getting rid of the malignant cells. In time, these healthy cells will start to grow again and most of the side effects will disappear.

Radiation, or radiotherapy, is another method of treating cancer. A person getting radiation for cancer will probably be treated by a radiation oncologist, someone who specializes in using radiation to kill cancer cells. Radiotherapy machines deliver powerful X-rays or high-energy electrons to the part of the body that's affected by cancer. After repeated doses of high levels of radiation, many cancerous tumors shrink or disappear.

Radiation therapy is generally painless, but there may be some side effect, such as fatigue, nausea, vomiting, or diarrhea. Some patients complain that the area of skin that's irradiated feels sunburned. But most of these side effects are temporary.

Coping With and Recovering From Cancer

Coping with cancer and cancer treatments can disrupt a person's life for a while. People with cancer often need to get support from lots of different places to take care of the things they have to get done. For example, teens with cancer may need the help of a home tutor to get schoolwork done and adults with cancer may need help with housework or their jobs. And lots of people talk to therapists or professional counselors about the emotional side of dealing with a health problem.

You may hear doctors talk about a prognosis for someone with cancer. A prognosis is an estimate of how well that person's treatment is working and how likely it is that the cancer will come back.

After surgery or treatment with radiation or chemotherapy, a doctor will do tests to see if the cancer is still there. If there are no signs of cancer, then that person is in remission. Remission is the goal when anyone with cancer goes to the hospital for treatment. Sometimes, additional treatment, such as chemotherapy, might be needed for a while to keep someone in remission and to keep cancer cells from coming back.