Ref Robbins 8/e p262;7/e p272; 9/e p267 Hamaomatous Polyps Hamaomatous polyps occur sporadically and as compo- nents of various genetically determined or acquired syn- dromes (Table 14-6). As described previously, hamaomas are disorganized, tumor-like growths composed of mature cell types normally present at the site at which the polyp develops. Hamaomatous polyposis syndromes are rare, but they are impoant to recognize because of associated intestinal and extraintestinal manifestations and the need to screen family members. Juvenile Polyps Juvenile polyps are the most common type of hamaoma- tous polyp. They may be sporadic or syndromic. In adults, the sporadic form sometimes is also referred to as an inflam- matory polyp, paicularly when dense inflammatory infil- trates are present. The vast majority of juvenile polyps occur in children younger than 5 years of age. Juvenile polyps characteristically are located in the rectum, and most manifest with rectal bleeding. In some cases, prolapse occurs and the polyp protrudes through the anal sphincter. Sporadic juvenile polyps are usually solitary but in persons with the autosomal dominant syndrome of juvenile pol- yposis the number varies from 3 to as many as 100. Colec- tomy may be required to limit the hemorrhage associated with polyp ulceration in juvenile polyposis. Dysplasia occurs in a small propoion of (mostly syndrome- associated) juvenile polyps, and the juvenile polyposis syn- drome is associated with increased risk for the development of colonic adenocarcinoma. hamaomatous polyps and mucocutaneous hyperpigA mentation that carries an increased risk of several malig- nancies, including cancers of the colon, pancreas, breast, lung, ovaries, uterus, and testes, as well as other unusual neoplasms. Germ line heterozygous loss-of-function muta- tions in the gene LKB1/STK11 are present in approximately half of the patients with the familial form of Peutz-Jeghers syndrome, as well as a subset of patients with the sporadic form. Intestinal polyps are most common in the small intestine, although they may also occur in the stomach and colon and, rarely, in the bladder and lungs. On gross evaluation, the polyps are large and pedunculated with a lobulated contour. Histologic examination demonstrates a characteristic arborizing network of connective tissue, smooth muscle, lamina propria, and glands lined by normal-appearing intestinal epithelium (Fig. 14-31, B