Tubular Adenoma with Low-Grade Dysplasia

Pathological Definition

The American Cancer Society defines all adenomas as containing some degree of dysplasia, which is divided into two categories: low-grade dysplasia and high-grade dysplasia 1, 2, 3
Low-grade dysplasia encompasses what was previously termed "mild" or "moderate" dysplasia, while high-grade dysplasia represents what was formerly classified as "severe dysplasia" or "carcinoma in situ" 1, 2, 3

The risk of malignancy or severe dysplasia in tubular adenomas with low-grade dysplasia is extremely low, particularly when the polyp is small, with a 0.6% risk of advanced neoplasia over 5 years of surveillance 1, 3, 4
Size is the most critical predictor of cancer risk, with large adenomas (≥10 mm) being 20.3 times more likely to harbor high-grade dysplasia compared to small adenomas 3, 4

Tubular adenomas with low-grade dysplasia are classified as "low-risk adenomas" when they meet specific criteria, including being 1-2 tubular adenomas, <10 mm in size, and having low-grade dysplasia only 1, 5
Patients with low-risk adenomas have only a small, nonsignificant increase in risk of advanced neoplasia within 5 years compared to individuals with no baseline neoplasia 5

For patients with 1-2 small tubular adenomas with low-grade dysplasia (<10 mm), the next colonoscopy should be performed in 7-10 years, based on evidence showing a low risk of advanced adenomas at 5-10 year follow-up 5
The rate of advanced adenomas at 5-10 year follow-up in low-risk adenoma patients is 5.2-6.2% 5

Villous or tubulovillous architecture confers a relative risk of 8.34 for subsequent advanced neoplasia, while high-grade dysplasia increases 5-year advanced neoplasia risk to 10.9% compared to 0.6% for low-grade dysplasia 1, 2, 3, 4
Proximal location carries an odds ratio of 1.65-2.69 for subsequent advanced adenomas 1, 3, 4

The American Gastroenterological Association suggests that large adenomas (≥10 mm) are 20.3 times more likely to harbor high-grade dysplasia compared to small adenomas 6
The National Comprehensive Cancer Network recommends that patients with five or more adenomas are classified as highest-risk, with 49% developing advanced adenomas at first follow-up 7
The American College of Gastroenterology states that high-grade dysplasia frequency increases from 4.4% in 6-10 mm adenomas to 16.2% in adenomas >10 mm 6

The American College of Gastroenterology recommends that low-risk patients (1-2 small tubular adenomas) have a next colonoscopy in 7-10 years 6
The National Polyp Study demonstrated that first follow-up can be safely delayed to 3 years for most patients with adenomas 8
The American Gastroenterological Association suggests that intermediate-risk patients (3-4 tubular adenomas <10 mm) have a next colonoscopy in 3-5 years 6, 9

The American Society for Gastrointestinal Endoscopy states that adequate bowel preparation is essential—inadequate preparation results in 35-36% miss rates for adenomas and advanced adenomas 10, 6
The American College of Gastroenterology recommends that complete cecal intubation must be documented—lack of cecal intubation increases odds of finding adenoma on subsequent examination 3.62-fold 10

The American Gastroenterological Association states that family history increases prevalence of adenomas at baseline colonoscopy 7
The National Comprehensive Cancer Network recommends that no evidence supports different surveillance recommendations for patients with family history who have adenomas, unless dominantly inherited syndromes are suspected 7