Thus the presence of adenomas places the patient as well as first-degree relatives in the high-risk category. The degree of malignancy is correlated with the size and type of adenoma, the position in the colon, and the age of the patient (10:242-243). Most adenomas larger than 1 cm will enlarge with time, and within 20 years one third of these become malignant. Thus it is recommended that all polyps that are greater than 0.5 cm should be removed. Furthermore a search for more should be initiated since there is a 30-50% likelihood of finding more polyps, and recurrence is possible, with 77% of recurrent polyps occurring at the site of excision.
Malignancy risk is greater in polyps that are close to a co-existing cancerous growth and/or occur in the distal colon (left side). Villous adenomas (cauliflower-like) are more likely than tubular to become malignant. Persons over 50 have a 30% chance of having adenomatous polyps, but only 3% have polyps larger than 1 cm.
An inherited tendency towards development of hundreds of adenomas is characteristic of several syndromes (hereditary adenomatous polyposis syndromes) (10:244-247). They are transmitted as autosomal dominant traits. Familial adenomatous polyposus coli syndrome virtually always results in colon cancer unless the colon is resec