Colitis-associated neoplasia: dysplasia in long-standing IBD
- Process
Years of colitis raise the risk of colon cancer, which often starts in flat abnormal lining that is hard to see.
What it is
Long-standing ulcerative colitis and colonic Crohn disease raise the risk of colorectal adenocarcinoma. The precursor is dysplasia, which often arises in flat mucosa rather than as a polyp, so surveillance relies on many biopsies and enhanced endoscopy. The molecular sequence differs from sporadic cancer: TP53 changes occur early and APC loss late.
Structure
- Dysplasia: crowded, elongated, hyperchromatic nuclei that reach the surface; high grade shows loss of polarity and complex glands.
- Distinguishing dysplasia from regenerative atypia in active inflammation is difficult; surface maturation favours reactive change.
Step by step
- Chronic inflammation exposes the epithelium to oxidants and repeated regeneration.
- Early TP53 mutation and chromosomal instability arise in flat mucosa.
- Low-grade dysplasia appears, often multifocal and hard to see.
- High-grade dysplasia develops; carcinoma may already be present nearby.
- Invasive adenocarcinoma, sometimes beneath only low-grade surface dysplasia.
Clinical notes
- Surveillance colonoscopy usually begins about eight years after diagnosis, earlier with primary sclerosing cholangitis.
- Sporadic adenomas also occur in IBD and can be hard to separate from polypoid colitis dysplasia.
Test yourself
Think of the answer, then tap the question to see it.
After how many years of colitis does cancer risk rise sharply?
About eight to ten years after onset.
Why is surveillance started at diagnosis in IBD patients with primary sclerosing cholangitis?
Their risk of colorectal neoplasia is higher than that of other IBD patients.
How does the molecular sequence of colitis-associated cancer differ from sporadic cancer?
TP53 changes tend to occur early and APC loss later, the reverse of the classic adenoma–carcinoma sequence.
Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Ulcerative Colitis (StatPearls (NCBI Bookshelf), 2025); Colorectal Cancer Screening (StatPearls (NCBI Bookshelf), 2025).
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Representative model, for educational purposes only.