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What is Cancer?

Cancer is a word that describes a wide range of similar diseases.  There are over 100 different types of cancer, but they all have a lot in common.11  Primarily, all cancers are an extreme growth of cells that your body can't stop or destroy.  These cell growths often spread from one part of the body to another, and they destroy normal, healthy cells. 

Most of the time, cancer cells will form clumps called tumors. Some tumors are cancer, and others ones are not.  Cancerous tumors are called "malignant," a word that means very dangerous.  Noncancerous tumors are called "benign," which is non-malignant. 

Some cancers, like leukemia, do not involve tumors at all and instead can grow in blood cells or other cells of the body.  

Cancer cells can start growing anywhere in your body.  Depending on where the cells are, cancer has a different name and is treated differently.  For example, cancer cells in your lungs are called lung cancer. Cancers in different parts of the body can be very different—some types of cancer grow and spread very quickly, while others grow and spread very slowly.  Doctors have good treatments for some forms of cancer, but few or no good treatments for other forms.


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