Cancer is not just one disease. There are many types of cancer. Cancer can start in many different places in the body. It can start in the lungs, the breast, the colon, or even in the blood. Cancers are alike in some ways, but they are also different in the ways they grow and spread. So when someone has cancer, the first question to think about is, "What kind of cancer do they have?"

How are cancers alike?

The cells in our bodies all have certain jobs to do. Normal cells divide in an orderly way. They die when they are worn out or damaged; then they are replaced with new cells. Cancer is a disease in which cells start to grow out of control. The cancer cells keep on growing and making new cells. They crowd out normal cells. This causes problems in the part of the body where the cancer started.

Cancer cells can also spread to other parts of the body. For example, cancer cells in the lung can travel to the bones and grow there. When cancer cells spread, it is called metastasis. When lung cancer spreads to the bones, it is still called lung cancer because that is where it started. It is not called bone cancer unless it started in the bones.

How are cancers different?

Some cancers tend to grow and spread very quickly. Others grow more slowly. They also respond to treatment in different ways. Some types of cancer are best treated with surgery. Others do better with drugs called chemotherapy (often called simply "chemo"). Often 2 or more treatments are given to get the best results.

When someone has cancer, the doctor will want to find out what kind of cancer it is. People with cancer need treatment that is aimed at their type of cancer.

What are tumors?

Most cancers form a lump that doctors call a tumor or a growth. Not all tumors (lumps) are cancer. Doctors have to take out a piece of the lump and look at it to find out if it is cancer. Lumps that are not cancer are called benign. Lumps that are cancer are called malignant.

There are also a few kinds of cancer, like leukemia (cancer of the blood), that do not form tumors. They grow in the blood or other cells of the body.

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Last Medical Review: 03/19/2008
Last Revised: 05/22/2009