II. Types: General
- Benign
- Hyperplastic Colonic Polyp (except the higher risk, hyperplastic polyposis syndrome)
- Inflammatory Colonic Polyp
- Malignant Potential (require complete excision and close interval follow-up)
- Adenomatous Colonic Polyp
- Sessile Serrated Adenomatous Colonic Polyp
III. Types: Hyperplastic Polyp
- Account for 50% of sigmoid and rectal polyps
- Small (1-5 mm), sessile polyps
- Rare dysplasia risk (does not modify Colonoscopy screening intervals)
IV. Types: Adenomatous Polyp
- Tubular adenomas (80%)
- Malignant transformation rate: 4-8%
- Tubulovillous adenoma
- Malignant transformation rate: 19%
- Villous adenoma
- Malignant transformation rate: 38.4%
V. Types: Sessile Serrated Adenomatous Polyp
- Precautions
- Primary pathway to hypermethylated gene cancers (20-30% of Colorectal Cancer)
- Must be completely excised and monitored as with adenomatous polyps
- Easily missed on Colonoscopy (flat, indiscrete lesions with adherent mucus)
- Higher malignant potential when proximal to the sigmoid colon
- Characteristics
- Typically larger than 1 cm, but typically flat
- Occurs in right colon in 75% of patients
- More common in women (65%)
- Accounts for 9% of all Colonic Polyps
- References
- Larson (2008) Mayo Selected Topics in Internal Medicine, Lecture
- Snover (2005) Am J Clin Path 124:380 [PubMed]
- Spring (2006) Gastroenterology 131: 1400-7 [PubMed]
VI. Interpretation
- Factors suggesting higher risk of future adenomatous polyp (3 year follow-up)
- Three or more adenomatous polyps
- Adenomatous polyp or serrated polyp >1 cm
- Polyp biopsy consistent with high grade dysplasia or villous features
- Sessile serrated polyp with dysplasia
- Traditional serrated adenoma
- Factors suggesting lower risk of future adenomatous polyp (5-10 year follow-up)
- High quality baseline exam (see Colon Cancer Screening with Colonoscopy)
- Fewer than 3 adenomatous polyps
- Small adenomatous polyps <1 cm
- No high grade or villous changes
- Adenomatous polyps removed completely (not piecemeal)
- References