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Flat adenomas of the colon
1Division of Anatomic Pathology, University of British Columbia, Vancouver, Canada.
Human Pathology
|January 1, 1991
Summary
Flat adenomas in the colon, often missed during colonoscopy, show a higher risk of high-grade dysplasia. These lesions may precede small, ulcerated colon cancers, warranting increased surveillance.
Area of Science:
- Gastroenterology
- Colorectal Cancer Research
- Pathology
Background:
- Flat adenomas are a recognized subtype of colonic adenomas.
- Their potential for high-grade dysplasia and association with early-stage cancers is an area of ongoing research.
Purpose of the Study:
- To investigate the clinicopathologic features of flat adenomas.
- To compare the rate of high-grade dysplasia in flat versus polypoid adenomas.
- To assess the association of flat adenomas with early colonic carcinomas.
Main Methods:
- Histologic review of 340 surgically or colonoscopically removed adenomas from 210 patients.
- Identification and characterization of 29 flat adenomas (≤1.0 cm radial diameter).
- Comparison of high-grade dysplasia rates between flat and polypoid adenomas.
Main Results:
- Twenty-nine flat adenomas were identified.
- Flat adenomas showed a significantly higher rate of high-grade dysplasia (41%) compared to polypoid tubular adenomas (4%).
- Two patients presented with concurrent flat, ulcerated colonic carcinomas without a clear polypoid precursor.
Conclusions:
- Flat adenomas may represent a distinct subtype with a propensity for rapid progression to high-grade dysplasia, even at small sizes.
- These lesions could be precursors to small, flat, ulcerated colonic carcinomas.
- Increased colonoscopic surveillance may be beneficial for patients diagnosed with flat adenomas.