What is colorectal cancer?
Colon cancer, or colorectal cancer, is cancer that starts in the large intestine (colon) or the rectum (end of the colon). In 2011 there were 460 new cases of colorectal cancer and 150 colon cancer related deaths in South Dakota. In that same time year, an estimated 141,210 newly diagnosed colorectal cancer cases and 49,380 colorectal cancer deaths occurred in the United States. This makes it one of the most common cancers. But unlike some cancer, colorectal cancer can often be cured by surgery and new treatments are making survival even more likely. The earlier the colorectal cancer is diagnosed, the greater the likelihood of cure.
Throughout our lives, the lining of the bowel constantly renews itself. This lining contains millions of tiny cells that grow. Each cell contains genes, which give instructions to the cell on how to behave. When genes behave in a flawed manner, this can cause the cells to grow too quickly, which eventually leads to the formation of a growth that is known as a polyp. This is the first signs of possible cancer.
What is a polyp?
A polyp starts as a tiny bump on the inside of the bowel. At first, the genes give instructions for the polyp to grow in an orderly manner. Some polyps remain very small throughout their lives while others slowly grow larger. At this stage, the lump is still benign. Most polyps remain benign throughout life but about one in 10 will turn into a cancer. Broadly speaking, the larger the polyp, the more likely it is to become cancerous. It is unusual for a polyp to be malignant if it is smaller than 1 centimeter in diameter.
It is believed that all malignancies of the bowel probably start off as benign polyps. Removing benign polyps can prevent cancer from developing later.
How does a polyp turn to cancer?
In some polyps, the instructions the genes give the cell on how to grow become increasingly disordered. When this happens, the cells grow so quickly and in such a strange way that they grow not just on the lining of the bowel but into the wall of the intestines. At that stage, the polyp becomes malignant, or cancerous. As the tumor advances, it grows through the wall of the bowel to invade nearby tissues and can spread more widely throughout the body, particularly to the liver and the lungs.