Cancer refers to any one of a large number of diseases characterized by the development of abnormal cells that divide uncontrollably and have the ability to infiltrate and destroy normal body tissue. Cancer often has the ability to spread throughout your body.

Cancer is the second-leading cause of death in the United States. But survival rates are improving for many types of cancer, thanks to improvements in cancer screening and cancer treatment.

What cancer looks like:

The image of the normal colon tissue, at left, shows well-formed oval-shaped glands, evenly lined with a single, organized layer of cells, indicated by arrows. The image of the cancerous colon tissue, in contrast, shows highly disorganized cancer cells stacked upon each other in an apparently random fashion.