Usually significant architectural and/or cytologic atypia
Usually lacks significant architectural and/or cytologic atypia (high grade dysplasia may be misplaced occasionally but is typically accompanied by bland adenoma tissue)
Inflammatory or fibrotic stroma
Infiltrates through muscularis mucosae
Frequently demonstrable continuity with surface through a gap in the muscularis mucosae
Hemosiderin restricted to head of polyp
Hemosiderin common in stalk stroma
Glands not accompanied by lamina propria
Glands may be accompanied by lamina propria
Usually infiltrative, non-circumscribed
May occur throughout the colorectum
Virtually restricted to left colon
Collagen type IV weak, discontinuous
Collagen type IV strong, continuous around epithelial nests
E cadherin markedly decreased staining compared to overlying adenoma
E cadherin same intensity as overlying adenoma (high grade dysplasia may show decrease)
No special significance to polyps with misplaced glands
Behavior, significance and therapy are simply that of the adenoma in which it occurs
The term misplaced is preferred over pseudoinvasion
It is less likely to be misinterpreted as needing aggressive therapy
Bosman FT, Carneiro F, Hruban RH, Thiese ND (Eds). WHO Classifiication of Tumors of the Digestive System, IARC, Lyon 2010.
Petersen VC, Sheehan AL, Bryan RL, Armstrong CP, Shepherd NA. Misplacement of dysplastic epithelium in Peutz-Jeghers Polyps: the ultimate diagnostic pitfall? Am J Surg Pathol. 2000 Jan;24(1):34-9.
Yantiss RK, Bosenberg MW, Antonioli DA, Odze RD. Utility of MMP-1, p53, E-cadherin, and collagen IV immunohistochemical stains in the differential diagnosis of adenomas with misplaced epithelium versus adenomas with invasive adenocarcinoma. Am J Surg Pathol. 2002 Feb;26(2):206-15.
Pascal RR, Hertzler G, Hunter S, Goldschmid S. Pseudoinvasion with high-grade dysplasia in a colonic adenoma. Distinction from adenocarcinoma. Am J Surg Pathol. 1990 Jul;14(7):694-7.
Muto T, Bussey HJ, Morson BC. Pseudo-carcinomatous invasion in adenomatous polyps of the colon and rectum. J Clin Pathol. 1973 Jan;26(1):25-31.
Yantiss RK, Goldman H, Odze RD. Hyperplastic polyp with epithelial misplacement (inverted hyperplastic polyp): a clinicopathologic and immunohistochemical study of 19 cases. Mod Pathol. 2001 Sep;14(9):869-75.