What is colorectal cancer?

Symptoms of colorectal cancer

Risk factors for developing colorectal cancer

What is colorectal cancer?

"Colorectal cancer" is a word used to group both cancer of the colon as well as cancer of the rectum under a single term. Together, the colon and rectum make up the large intestine. The large intestine is the end or most distal part of the gastrointestinal tract where food contents traverse from the esophagus ---> stomach ---> small intestine ---> large intestine. While the stomach and small intestine are primarily involved in digestion and absorption of nutrients, the primary function of the large intestine is to absorb water and to store undigested food waste or stool until it can be evacuated. The colon consists of the cecum, ascending, transverse, descending, and sigmoid portions; the rectum consists of the lowest 10-15 cm of the large intestine which stores solid fecal waste until it is evacuated out of the anus.

Cancer of the colon or rectum is an abnormal and malignant mass of rapidly proliferating cells which originate from the normal inner lining cells of the large intestine known as mucosal cells. These cancers are characterized by cells that 1) continuously multiply without regard to normal control mechanisms of the body, 2) often invade local adjacent structures or grow to sufficient size to cause colonic obstruction, or 3) spread to distant parts of the body (metastases) where they may disrupt function of other organs such as the liver or brain. Colorectal cancer frequently becomes necrotic, ulcerates and bleeds and often, microscopic bleeding is present long before the patient develops symptoms. Today, the only known cure for this disease is to detect it at an early stage and to resect the tumor.

A "polyp" is smaller, often rounded mass of abnormally proliferating cells of the intestinal lining and is felt to represent the earliest stages of colorectal cancer development. Cells making up the polyp can be either benign adenomas (i.e. non-malignant) or cancerous adenocarcinomas (i.e. malignant) or a mixture of the two types of cells. Removal of benign colon polyps has been recently shown to reduce the likelihood of subsequent cancer of the colon.

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