Genetics of Colonic Polyposis

A 38-year-old otherwise healthy man undergoes a colonoscopy for a history of hematochezia. A 4-cm exophytic mass in the lower rectum and approximately 10–15 polyps from 5 to 15 mm in size, predominantly in the descending and sigmoid colon, are noted. The rectal mass is found to be an adenocarcinoma on biopsy examination and is staged as T2N0 by endoscopic ultrasound. Multiple polyps removed at colonoscopy are adenomatous, with 2 displaying high-grade dysplasia. A 51-year-old brother had a total proctocolectomy with ileal pouch–anal anastomosis (IPAA) for colonic polyposis at age 39; more than 100 colonic polyps were present. Genetic testing for familial adenomatous polyposis (FAP) was not available at the time of his brother’s surgery. Five other siblings (ages, 32–49 y) and the patient’s mother (age, 69 y) have had normal colonoscopic examinations. The patient’s father died at age 62 without a prior colon examination. No other history of familial cancer is apparent.