Adenomas by definition have at least low grade dysplasia
Low grade dysplasia thus need not be addressed in the report for the typical adenoma
Moderate dysplasia is not an accepted term
Anything less than high grade should be termed low grade
The term moderate dysplasia has no accepted meaning and risks giving an unclear clinical message
High grade dysplasia is characterized by any one of the following:
Back to back gland lumens without intervening stroma
Should clearly be a manifestation of total loss of polarity by atypical cells
Frequently, well differentiated mucin producing cells will pile up, forming lumens, technically appearing cribriform
Nuclei show regular basal orientation
Nuclei typically not markedly enlarged
This should not be considered high grade dysplasia
Severe cytologic atypia
This is unusual in the absence of cribriform architecture, but can occur
Invasion with a desmoplastic response
Invasion confined to the lamina propria including muscularis mucosae is designated high grade intramucosal neoplasia
At other GI sites this is considered intramucosal carcinoma
If that term is used for colorectal lesions, the report should make it clear that it represents an in situ lesion
Significance of high grade intra-mucosal invasive carcinoma is a subject of current debate
In a series of 15 such cases, all appeared to be adequately treated by polypectomy (Lewin 2007)
Two cases exhibiting aggressive features have subsequently been reported (Shia 2008)
Use TNM staging if high grade dysplasia or invasive carcinoma are present
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Lewin MR, Fenton H, Burkart AL, et al. Poorly differentiated colorectal carcinoma with invasion restricted to lamina propria (intramucosal carcinoma): a follow-up study of 15 cases. Am J Surg Pathol. 2007;31:1882-1886.
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