The evolution of cancer of the colon and rectum

TLDR

Adenomas of the colon and rectum vary in malignant potential based on size, histology, and atypia, with small adenomatous polyps having low risk and villous adenomas larger with higher cancer rates, and the polyp‑cancer sequence evolves slowly. The study discusses how the polyp‑cancer sequence informs cancer prevention program design and etiological research of large bowel cancer. Evidence indicates that most colorectal cancers arise via the polyp‑cancer sequence, although most adenomas never become cancerous during a normal adult lifespan.

Abstract

The malignant potential of adenomas of the colon and rectum varies with size, histological type and grade of epithelial atypia. The adenomatous polyp is usually small and has a low malignant potential, whereas tumors with a villous structure are usually larger and have a much higher cancer rate. Severe atypia is more common in villous adenomas than in adenomatous polyps. Evidence is presented which suggests that most cancers of the colon and rectum have evolved through the polyp-cancer sequence although the majority of adenomas do not becoma cancerous during a normal adult life span. The slow evolution of the polyp-cancer sequence is stressed. The implications of the polyp-cancer sequence for the design of cancer prevention programmes and the study of the aetiology of large bowel cancer are discussed.