Which of the following has the highest potential of progression into cancer
Correct Answer: Adenomatous polyp
Description: Familial adenomatous polyposis Familial adenomatous polyposis (FAP) is defined clinically by the presence of more than 100 colorectal adenomas, but is also characterised by duodenal adenomas and multiple extraintestinal manifestations. Over 80% of cases come from patients with a positive family history. The remainder arise as a result of new mutations in the adenomatous polyposis coli (APC) gene on the sho arm of chromosome 5. FAP is inherited as an autosomal dominant condition and is consequently equally likely in men and women. The lifetime risk of colorectal cancer is 100% in patients with FAP. FAP can also be associated with benign mesodermal tumours such as desmoid tumours and osteomas. Epidermoid cysts can also occur (Gardner's syndrome); desmoid tumours in the abdomen spread locally to involve the intestinal mesentery and, although non-metastasising, they may become unresectable. Up to 50% of patients with FAP have congenital hyperophy of the retinal pigment epithelium (CHRPE), which can be used to screen affected families if genetic testing is unavailable. CLINICAL FEATURES Polyps are usually visible on sigmoidoscopy by the age of 15 years and will almost always be visible by the age of 30 years. Carcinoma of the large bowel develops 10-20 years after the onset of the polyposis. If there are no adenomas by the age of 30 years, FAP is unlikely. If the diagnosis is made duringadolescence, surgery is usually deferred to the age of 17 or 18 years unless symptoms develop. Malignant change is rare before the age of 20 years. Examination of blood relatives, including cousins, nephews and nieces, is essential; a family tree should be constructed and a register of affected families maintained. Referral to a medical geneticist is essential. If over 100 adenomas are present at colonoscopy, the diagnosis can be made confidently Ref: Bailey and love 27th edition Pgno : 1259
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