Cancer starts when cells in the body change (mutate) and grow out of control. These cells can form lumps of tissue called tumors. Cancer that starts in the cells of the colon is called colon cancer. Cancer that starts in the cells that make up the rectum is called rectal cancer. These cancers are a lot alike, so they're sometimes just called colorectal cancer.
Understanding the colon and rectum
The colon and rectum make up the large intestine (also called the large bowel). The colon is a muscular tube that's about 5 feet long. It forms the last part of the digestive tract. It absorbs water and stores food waste. The rectum is the last 6 inches of the large intestine.
The colon and rectum have a smooth inner lining made of millions of cells. These cells replace themselves everyday to keep the lining healthy. Changes in these cells can lead to growths in the colon and rectum that can become cancer.
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