Table 1

Clinical features of the major classes of colorectal lesions (conventional adenomas and the serrated class)

LesionFrequency in screening37Colonic distribution1415DysplasticMalignant potentialShapeSurface features12
Conventional adenomas∼50%ThroughoutYYUsually sessile or flat
5%–10% pedunculated
<1% depressed
Rich in blood vessels surrounding pits.
Pits of variable size and shape, often tubular
Serrated class
 Hyperplastic polyp∼30%Mostly distalNNSessile or flatNo surface vessels or only a few lacy vessels.
Pits of relatively uniform size and shape
 Sessile serrated polypMostly proximal
 Without cytological dysplasia3%–8%NY
 With cytological dysplasia<1%YYMay have surface features of both the serrated class and the conventional adenomas
 Traditional serrated adenomarareMostly distalYYSessile or pedunculatedVilliform