Fap

The striking number of adenomatous polyps that often carpet the colon and the 100% lifetime risk of CRC characterize FAP. The average age of colorectal polyp formation is 16 years and of CRC is 39 years (Burt and Jacoby, 2003). The adenomatous polyposis coli (APC) gene is mutated in FAP, and patients inherit the disease in an autosomal dominant fashion, though about one-third of patients have no known family history and presumably are new mutation carriers. The frequency of FAP in the general population is about 2 to 3 in every 100,000 persons; the disease accounts for < 1% of all CRCs.

The diagnosis of classical FAP is often clinically apparent due to the profound phenotype these patients have. The number of colonic polyps in FAP can vary from family to family and even within families, although, typically, the numbers are in the thousands in fully expressed disease (Burt and Jacoby, 2003). The polyps are characteristically adenomatous and are usually small (< 1cm). In the upper GI tract, polyps can line the entire stomach. Polyps in the corpus and fundus are usually fundic gland polyps, though adenomatous polyps can arise in these locations as well. Polyps in the antrum tend to be adenomatous and, therefore, deserve special attention. Duodenal polyps are usually adenomatous and have a predilection for the duo denal papilla. As a consequence, cancers on or around the papilla are the most frequent GI cancers in FAP patients who have had a colectomy. Polyps in other areas of the small bowel (SB) are less frequent, but are known to occur in FAP and exhibit an associated risk of SB cancer.

Besides GI manifestations, patients with FAP have several other clinical findings. These include benign growths with little clinical significance, such as osteomas (bony cysts found usually in the mandible, skull), abnormal dentition, congenital hypertrophy of the retinal epithelium and several skin findings, especially epidermoid cysts and fibromas. Other extra-intestinal manifestations, however, can have more important clinical implications. Desmoid tumors are benign growths of fibrous tissue that can occur intra-abdominally or extra-abdominally. Though not invasive, desmoid tumors can enlarge and impinge on adjacent structures, such as bowel, vasculature, and nerves, causing a high degree of morbidity. The phenotype of FAP varies in different families and has been associated with the different mutation locations within the APC gene. Associated malignancies besides colon cancer (although all exhibit < a 2% lifetime risk), include SB cancer, stomach cancer, pancreatic cancer, thyroid cancer, hepatoblastoma (mostly in children), brain cancer, adrenal carcinomas, and, rarely, biliary tract cancers.

Variants of FAP include Gardner's syndrome, Turcot's syndrome (TS) and attenuated adenomatous polyposis coli (AAPC). The former is associated with several extraintestinal growths, such as desmoids, fibromas, and osteo-mas. TS is associated with FAP together with central nervous system tumors in about two-thirds of families. Interestingly, the other one-third have hereditary non-polyposis CRC. AAPC will be described later.

Management of patients with FAP focuses on several important clinical decisions, including treatment options and cancer surveillance. Though colectomy is indicated as prophylaxis to prevent the otherwise inevitable development of CRC, the age to perform the surgery and what surgery to perform can be potential issues. We usually wait until patients are postadolescence before performing colec-tomy as the psychosocial impact tends to be less significant at later ages although sometimes polyp severity requires earlier surgery. Surgical options include total colectomy with ileal pouch-anal anastamosis (IPAA) and subtotal colectomy. The latter procedure leaves a rectal remnant that requires periodic endoscopic examinations and polyp ablation. Total colectomy with IPAA removes the rectal mucosa, though there is potential to develop ileal polyps (usually lymphoid hyperplasia, but sometimes adenomas) warranting periodic surveillance of the terminal ileum.

Duodenal polyps can pose therapeutic challenges to the endoscopist and surgeon. Smaller ampullary tumors can be managed endoscopically with papillectomy. However, larger lesions need to be removed surgically. Gastric polyps

(Figure 95-1) are usually fundic gland polyps, but some can be adenomatous and require removal. We usually remove larger polyps (> 1 cm), antral polyps or polyps that appear endoscopically unique from the other polyps, including those that are reddish in appearance (Figure 95-2).

Medical management has a potential role in controlling adenomas. Nonsteroidal anti-inflammatory drugs and selective cyclooxygenase-2 inhibitors have both been shown to reduce the number of colorectal polyps in patients with FAP (Giardiello et al, 1993; Steinbach et al, 2000) and may be used to assist in management in patients who have a remaining rectum.

Because patients with FAP are at higher risk for several malignancies, regular surveillance for malignancy is recommended and is important not to overlook. Tables 95-1 and 95-2 outline the suggested surveillance strategies and intervals for each of the potential malignancies in FAP (McGarrity et al,2000).

FIGURE 95-1. Carpeting of polyps in the stomach of a patient with familial adenomatous polyposis. The vast majority of these are fundic gland polyps.
FIGURE 95-2. A large sessile tubulovillous adenoma beneath the gastroesophageal junction in a patient with familial adenomatous polyposis.
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