Are polyps the same as adenomas?

Are Polyps the Same as Adenomas?

No, polyps and adenomas are not the same—"polyp" is a broad descriptive term for any mass protruding into the colon lumen, while "adenoma" is a specific type of neoplastic polyp with malignant potential. 1

Understanding the Terminology

A polyp is simply a physical description of any tissue mass projecting into the bowel lumen, regardless of its microscopic composition. 1 Think of "polyp" as describing what you see endoscopically—it tells you nothing about cancer risk.

Adenomas, by contrast, are a specific histologic subtype of polyp that are neoplastic (precancerous) and represent the primary pathway to colorectal cancer. 2, 3 This is a critical distinction because management depends entirely on the histologic type, not just the presence of a polyp.

Major Categories of Colon Polyps

Neoplastic Polyps (Precancerous)

Adenomatous polyps are the most clinically important category, representing one-half to two-thirds of all colorectal polyps and carrying established malignant potential through the adenoma-carcinoma sequence. 3 These include:

• Tubular adenomas (>80% tubular elements): Most common type of adenoma 2
• Villous adenomas (>80% villous elements): Higher malignancy risk 2
• Tubulovillous adenomas (mixed architecture): Intermediate risk 2

Serrated polyps with precancerous potential account for up to 30% of colorectal cancers and include sessile serrated polyps (SSPs) and traditional serrated adenomas. 2, 3 SSPs are found in 8-9% of screening colonoscopies, predominantly in the proximal colon, and are more difficult to detect than conventional adenomas due to their flat morphology and lack of surface blood vessels. 2

Non-Neoplastic Polyps (Generally Benign)

Small, distally located hyperplastic polyps carry no increased colorectal cancer risk and patients should be rescreened as average-risk individuals. 2, 4 However, this is where clinical judgment becomes critical:

• Large (≥1 cm), sessile, proximally located hyperplastic polyps with atypical features may progress to cancer through the serrated pathway and warrant surveillance similar to adenomas. 2, 4
• Inflammatory polyps (related to IBD or other inflammation) 1
• Hamartomatous polyps (seen in polyposis syndromes) 1

Critical Clinical Pitfalls

The majority of polyps ≥10 mm are adenomas, and biopsy is not necessary to determine if colonoscopy is indicated for removal. 2 This is important because:

• Even diminutive polyps (≤5 mm) have a 10% rate of advanced histology when they are adenomas 5
• 69% of advanced adenomas are actually <10 mm in size 5
• Size correlates with malignancy risk: diminutive polyps have 0.05% cancer/high-grade dysplasia rate, while polyps ≥25 mm have a 22.5% rate 3

Hyperplastic polyposis syndrome requires recognition: ≥5 hyperplastic polyps proximal to sigmoid (with 2 >1 cm), any number of proximal hyperplastic polyps with affected first-degree relative, or >30 hyperplastic polyps throughout the colon. 2, 4 These patients have increased colorectal cancer risk, likely through the serrated adenoma pathway. 2

Practical Management Algorithm

All adenomatous polyps warrant removal and surveillance, regardless of size, because even small adenomas can harbor advanced histology. 3 The key decision points are:

1. Remove all adenomas completely 3
2. Remove all serrated polyps except diminutive rectal hyperplastic polyps 3
3. Remove any polyp with concerning features: size ≥10 mm, villous histology, or dysplasia 3
4. Document size (mm), number, location, and morphology clearly for surveillance planning 2, 4

Patients with only small distal hyperplastic polyps should return for colonoscopy in 10 years as average-risk individuals. 4 However, large, proximal, or atypical hyperplastic polyps require intensified surveillance similar to adenomas. 4