[Hereditary colorectal cancer associated with polyposis syndromes]

This study reviews different aspects of hereditary colorectal cancer associated with three polyposis syndromes: familial adenomatous polyposis, juvenile polyposis coli and Peutz-Jeghers syndrome. All these syndromes share some similarities: low incidence, autosomal dominant inheritance, genetic predisposition to colorectal cancer and/or other extracolonic cancers. Classical familial adenomatous polyposis is clinically defined by the presence of hundreds of adenomatous polyps in the colon and rectum, whereas less than 100 polyps are found in attenuated familial adenomatous polyposis. Without prophylactic colectomy, colorectal cancer develops inevitably by the age of 40. Restorative proctocolectomy with ileal anal-pouch anastomosis is the operation of choice in familial adenomatous polyposis. In juvenile polyposis coli, 50-200 hamartomatous polyps are found in the colon, rectum, stomach and small bowel. Life-time cumulative risk for colorectal cancer is estimated to be 50%. Prophylactic colectomy is required only in cases in which endoscopic surveillance is not able to control polyp development. Hereditary mixed polyposis syndrome is a variant form of juvenile polyposis coli, consisting of multiple mixed adenomatous, hyperplastic and hamartomatous polyps. Peutz-Jeghers syndrome is characterized by multiple hamartomatous polyps located in the small bowel, colon and stomach. Small bowel follow through and colonoscopy is advised for surveillance. Surgery is warranted only in cases of polyps larger than 1 cm. The causative genes of these syndromes have been cloned. Molecular genetic testing of affected and at-risk individuals is proposed in order to advise surveillance and management.