TuberoussclerosisInfancytoTSC1,TSC2 Hamartomatouspolyps(rectal)Facialangiofibroma,corticaladulthood tubers,renalangiomyolipoma development of several malignancies, including cancers of the colon, pancreas, breast, lung, ovaries, uterus, and testes, as well as other unusual neoplasms. Germ line loss-of-function mutations in the LKB1/STK11 gene 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. LKB1/STK11 encodes a tumor suppressive protein kinase that regulates cellular metabolism, yet another example of links between alterned metabolism, abnormal cell growth, and cancer risk. 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. 15.31B
Colonic hyperplastic polyps are common epithelial proliferations that typically are discovered in the sixth and seventh decades of life. The pathogenesis of hyperplastic polyps is incompletely understood, but formation of these lesions is thought to result from decreased epithelial cell turnover and delayed shedding of surface epithelial cells, leading to a “pileup” of goblet cells. Although these lesions have no malignant potential, they must be distinguished from sessile serrated adenomas, histologically similar lesions that have malignant potential, as described later.
MORPHOLOGYHyperplasticpolypsaremostcommonlyfoundintheleftcolonandtypicallyarelessthan5mmindiameter.Theyaresmooth,nodularprotrusionsofthemucosa,oftenonthecrestsofmucosalfolds.Theymayoccursinglybutmorefrequentlyaremultiple,particularlyinthesigmoidcolonandrectum.Histologically,hyperplasticpolypsarecomposedofmaturegobletandabsorptivecells.Thedelayedsheddingofthesecellsleadstocrowdingthatcreatestheserratedsurfacearchitecture,the morphologichallmarkoftheselesions(Fig.15.32
The most common and clinically important neoplastic polyps are colonic adenomas, benign polyps that give rise to a majority of colorectal adenocarcinomas. Most adenomas, however, do not progress to adenocarcinoma.
Colorectal adenomas are characterized by the presence of epithelial dysplasia. These growths range from small, often pedunculated polyps to large sessile lesions. There is no gender predilection, and they are present in nearly 50% of adults living in the Western world beginning at age 50. Because these polyps are precursors to colorectal cancer, current recommendations are that all adults in the United States undergo screening colonoscopy starting at 50 years of age. Because individuals with a family history are at risk for developing colon cancer earlier in life, they are typically screened at least 10 years before the youngest age at which a relative was diagnosed. While adenomas are less common in Asia, their frequency has risen (in parallel with an increasing incidence of colorectal adenocarcinoma) as Western diets and lifestyles become more common.
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ABABFig. 15.31 Hamartomatouspolyps.(A)Juvenilepolyp.Notethesurfaceerosionandcysticallydilatedcryptsfilledwithmucus,neutrophils,anddebris.(B)Peutz-Jegherspolyp.ComplexglandulararchitectureandbundlesofsmoothmusclehelptodistinguishPeutz-Jegherspolypsfromjuvenilepolyps.