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Colorectal carcinogenesis: historical review
1Department of Surgical Oncology, Graduate School of Medicine, The University of Tokyo, Japan.
Diseases of the Colon and Rectum
|October 23, 1997
Summary
The understanding of colorectal cancer development has evolved, revealing new precursor lesions beyond traditional adenomas and highlighting distinct molecular pathways in nonpolypoid colorectal neoplasms.
Area of Science:
- Gastroenterology
- Oncology
- Molecular Biology
Background:
- The concept of colorectal carcinogenesis has evolved significantly over the past two decades.
- Historical reviews trace this evolution through distinct research periods.
Observation:
- Early research focused on large adenomas as primary colorectal cancer precursors.
- Subsequent studies identified smaller, nonpedunculated adenomas as significant precursors.
- The discovery of nonpolypoid neoplasms, including flat and depressed types, revealed previously unrecognized precursors.
Findings:
- Molecular biology studies revealed a lack of K-ras mutations in nonpolypoid neoplasms, suggesting a novel carcinogenic pathway.
- This contrasts with the established pathway for polypoid neoplasms.
- Nonpolypoid neoplasms, particularly depressed types, represent a distinct route in colorectal carcinogenesis.
Implications:
- The traditional adenoma-carcinoma sequence requires re-evaluation in light of new precursor findings.
- Understanding the distinct genetic alterations in nonpolypoid neoplasms is crucial for accurate diagnosis and treatment.
- Further research is needed to clarify the genetic basis of de novo colorectal carcinomas.