Pedunculated polypPedunculated polyp showing pseudo-invasion of stalk. Glands are present in the submucosa of the polyp head and stalk deep to the muscularis mucosae. The glands are associated with stroma identical to adenoma mucosal stroma, and distinct from the fibrous stroma characteristic of invasive adenocarcinoma. The dysplasia of the glandular elements in the stalk in pseudo-invasion may be low or high grade (in this case, low grade). Other features that suggest pseudo-invasion include hemosiderin deposits and pools of acellular mucin. Pseudo-invasion is likely to represent a manifestation of polyp prolapse and is seldom if ever encountered in sessile or flat adenomas.
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