Origin

Colorectal cancer (or Bowel cancer) refers to all malignant tumors that start in the colon or the rectum.

Colon - the muscular tube that constitute most of the large intestine Rectum - the final 10-15 cms of the large intestine, just before the anus.

Most colorectal cancers develop slowly throughout many years, often from small benign (non-cancerous) growths called polyps that degenerate into cancer.

A tiny percentage of colorectal cancers, mostly those that are hereditary, are associated with large numbers of polyps.

Virtually all colon cancers develop from polyps, and that is why all polyps detected should be removed and analyzed.

Polyps

A polyp is an abnormal tissue growth, usually in the shape of a small mushroom attached to the intestine’s inner wall. Other shapes exist, as is the case of flat polyps, but are rare.

Like all carcinomas, which develop from the tissues covering the surfaces of the body, polyps grow from the epithelium that internally coats the intestine after one (or more) of its cells mutate. 

Not all polyps lead to colorectal cancer, but as much as 95% of colorectal cancer cases originate in them. As a result, all polyps should be removed and analyzed in order to prevent disease. This is a very simple process, done by colonoscopy.

On the other hand, if a polyp is not removed it can degenerate into cancer. If the cancer is allowed to grow, it can eventually invade the walls of the colon and/or rectum and spread the disease through the blood or lymphatic system to other organs (e.g., liver, lungs, or ovary metastases). Once this happens is much more difficult to treat the disease.

Learn more about one of the most common cancers in the world:

• where it is found in the body , its  geographic distribution , as well as  different types of tumors  and  their classification .