Colorectal Carcinoma and Colonic Polyps
Colonic polyps – also known as colon polyps, should be suspected in any patient over 40 years of age who has gastrointestinal bleeding or a change in bowel habits. Often, the patient is completely without symptoms, but may complain of a change in bowel habits, abdominal pain, or of passing mucus through the rectum. Colonic polys are very common, occurring in 30% of patients 60 plus years of age. It is believed that all cancers of the colon (except those associated with ulcerative colitis) arise from these benign epithelial tumors. It generally takes a minimum of five years for an early polyp to become an invasive colorectal cancer. Most surgically removed colonic polyps are adenomatous polyps. Consequently, the removal of colonic polyps before they become malignant, has the potential of preventing the occurrence of a colorectal cancer in predisposed individuals.
The risk of colonic polyps becoming malignant is related to their histological type and size. There are 4 types of colonic polyps: hyperplastic, harmartomas, inflammatory. and adenomatous polyps. The most common type in adults, hyperplastic polyps, have virtually no malignant potential along with the inflammatory polpys. Adenomatous polpys, on the other hand, definitely carry a risk of malignant transformation that increases as they increase in size. Adenomatous polyps (adenomas) are further subdivided microscopically as tubular, villous, or tubulo-villous. A villous adenoma over 2 cm in size, has a greater than 50% risk of cancer. If the cancer remains confined to the mucosa of the polyp (carcinoma in situ) then a colonoscopic polypectomy is curative. If however the cancer has infiltrated the stalk of the polyp, then surgery is indicated. Also, because cancerous change in a polyp maybe localized, single biopsies of a polyp is not sufficient to eliminate the possibility of colorectal cancer; the entire polyp must be removed.
Once a polyp has been detected careful monitoring for additional polyps is indicated. The most common screening method, fecal occult testing, should be performed yearly to examine for occult blood in the patients stool. Even when the stools are negative for blood, periodic evaluation of the colon is still recommended. Sigmoidoscopy is often performed along with yearly fecal occult testing. There is some indication that this reduces colorectal cancer mortality. Colonoscopy or barium enema should be repeated in a year and then every 3 to 5 years if follow up examinations reveal no further colonic polyps.
In some patients there are hundreds of adenomatous polyps blanketing the colon. These multiple polyposis syndromes are rare, inherited abnormalities with significant risk for malignant potential. Gardner syndrome, familial polyposis and Turcot syndrome are all associated with multiple adenomatous polyps of the colon. They all carry a high risk of development of cancer. An individual with a colonic polyposis syndrome should be distinguished from conditions associated with juvenile polyps or hamartomatous polyps that are of low malignant potential.
