What is a hyperplastic polyp?

Hyperplastic Polyps: Definition and Clinical Significance

Hyperplastic polyps are the most common non-neoplastic lesions found during colonoscopy, typically small (0.5-1.5 cm) and located in the distal colon, with most small distally located hyperplastic polyps having little to no malignant potential. 1

Types and Characteristics

Hyperplastic polyps have the following characteristics:

• Most commonly found in the rectosigmoid region
• Typically small and sessile (less than 5mm)
• Account for 18-70% of all colonic polyps 1
• Generally considered benign when small and distally located

However, it's important to understand that hyperplastic polyps are not a homogeneous group:

Standard Hyperplastic Polyps

• Small (<5mm)
• Distally located (rectosigmoid)
• No dysplasia
• Low malignant potential
• Require no special surveillance beyond routine screening 2

Concerning Hyperplastic Polyps

• Large (>1cm)
• Proximally located (right colon)
• Sessile appearance
• May show atypical architectural and cytologic features 2
• May progress to serrated adenomas with potential for malignant transformation

Clinical Management

Management depends on polyp characteristics:

1. Small distal hyperplastic polyps:

   • No increased risk for colorectal cancer
   • Should follow standard average-risk screening intervals (10 years) 2, 1
   • No special surveillance required

2. Large or proximal hyperplastic polyps:

   • Complete removal is recommended
   • May warrant surveillance similar to adenomatous polyps 2
   • Higher risk of progression through serrated pathway to cancer

3. Hyperplastic polyps with atypical features:

   • May evolve into serrated adenomas
   • Associated with microsatellite instability (MSI) adenocarcinoma
   • Require complete removal and surveillance 2

Hyperplastic Polyposis Syndrome

This is a distinct clinical entity defined by the World Health Organization as:

• At least 5 histologically diagnosed hyperplastic polyps proximal to sigmoid colon (with 2 > 1cm), OR
• Any hyperplastic polyps proximal to sigmoid in a patient with first-degree relative with hyperplastic polyposis, OR
• More than 30 hyperplastic polyps throughout the colon 2, 1

Patients with hyperplastic polyposis syndrome have a significantly increased risk of colorectal cancer (up to 54% in some studies) 3 and require intensive surveillance.

Molecular Pathways and Cancer Risk

Recent evidence suggests some hyperplastic polyps may have malignant potential through:

• Aberrant DNA methylation
• BRAF mutations
• Microsatellite instability
• Mismatch repair deficiency 2

These molecular changes may lead to the development of serrated adenomas and eventually colorectal cancer through an alternative pathway distinct from the traditional adenoma-carcinoma sequence.

Important Clinical Considerations

1. Documentation: Complete documentation of size, location, and appearance of all polyps is essential for appropriate management 1

2. Terminology evolution: Terms like "sessile serrated adenoma" or "serrated polyp with abnormal proliferation" may be used for hyperplastic polyp variants with concerning features 2

3. Risk factors for neoplastic progression: Multiple polyps, large size (>1cm), and proximal location 4

4. Surveillance pitfalls: Proximal hyperplastic polyps may be flat and easily missed during colonoscopy 2

By understanding the spectrum of hyperplastic polyps and their potential clinical significance, clinicians can appropriately manage these common findings and identify patients who may require more intensive surveillance.