Colorectal adenomas: time for reappraisal

Area of Science:

• Gastroenterology
• Pathology
• Oncology

Background:

• Colorectal adenomas are typically classified as tubular or villous, with a mixed phenotype also recognized.
• Serrated and microtubular adenomas are less common histologic phenotypes that have not been consistently included in major studies.

Purpose of the Study:

• To classify colorectal adenomas into five distinct histologic categories: tubular, villous, mixed, serrated, and microtubular.
• To analyze the distribution and cell proliferation characteristics of these adenoma phenotypes.
• To advocate for the inclusion of serrated and microtubular adenomas as independent phenotypes in future research.

Main Methods:

• Histologic classification of 3135 colorectal adenomas diagnosed between 1993 and 2000.
• Analysis of adenoma location (colon vs. rectum).
• Assessment of cell proliferation patterns within the dysplastic glands/crypts of each phenotype.

Main Results:

• The study identified 66% tubular, 9% villous, 18% mixed, 6% serrated, and 1% microtubular adenomas.
• Over 80% of tubular, villous, serrated, and microtubular adenomas were located in the colon; none of the microtubular adenomas were found in the rectum.
• Distinct cell proliferation patterns were observed: upper glands (tubular, villous), lower crypts (serrated), and deeper rings (microtubular).

Conclusions:

• Serrated and microtubular adenomas possess unique morphologic and cell-proliferative characteristics that support their classification as independent phenotypes.
• It is recommended that serrated and microtubular adenomas be routinely included in future histologic classifications of colorectal polyps to enable better frequency comparisons.