The term "colorectal" is a contraction of two terms, 'colon' and 'rectum'. Parts of the digestive system, the colon is the name given to the last six or so feet of the intestine (otherwise known as the large intestine), and the rectum is the name for the last several inches of the large intestine just before it exits the body via the anus.
Colorectal cancer occurs when abnormal tissues, known as polyps, grow on the inner walls of the colon or rectum. Polyps often grow as a projection of tissue away from the colon wall, remaining connected to the colon wall by way of a thin stalk. Their shape is similar to that of a mushroom. Polyps are fairly common, especially in older people. The vast majority of polyps are not cancerous. However, some percentage of polyps become cancerous. Unchecked, a cancerous polyp gives rise to a tumor, which grows in size until it penetrates the bowel wall and involves adjacent organs and lymph nodes through the process known as metastasis.
Colorectal cancer is the third most prevalent cancer in the United States and, when undetected and untreated, the second most deadly. Approximately 130,000 new cases of colorectal cancer are diagnosed each year, and about 50,000 Americans die each year from colorectal cancer. While these statistics are alarming, it is important to remember that if caught early enough, colorectal cancer can often be cured. Early detection and removal of polyps can even prevent pre-cancerous polyps from becoming cancerous.