What is the recommended classification system for colorectal polyps, specifically the Nice (Narrow-Band Imaging International Colorectal Endoscopic) classification?

NICE Classification for Colorectal Polyps

The NBI International Colorectal Endoscopic (NICE) classification is the recommended system for classifying colorectal polyps as it provides accurate differentiation between polyp types without requiring magnification endoscopy and has been validated in multiple studies. 1

NICE Classification System Overview

The NICE classification, proposed in 2009 by the Colon Tumor NBI Interest Group, categorizes colorectal polyps into three types:

• Type 1 (Serrated Class): Represents hyperplastic polyps or sessile serrated polyps 1

  • Color: Pale
  • Vessels: Invisible
  • Surface pattern: Regular dark or white spots 1

• Type 2 (Conventional Adenoma): Represents conventional adenomas 1

  • Color: Browner relative to background
  • Vessels: Regular caliber, brown vessels surrounding white structures
  • Surface pattern: Regular tubular or branched/papillary pattern similar to surrounding mucosa 1

• Type 3 (Deep Submucosal Invasive Cancer): Represents lesions with deep submucosal invasion 1

  • Color: Brown to dark brown relative to background
  • Vessels: Disrupted or missing vessels
  • Surface pattern: Amorphous or absent pattern 1

Clinical Significance and Application

The NICE classification has several important clinical advantages:

• Can be used with or without magnification endoscopy 1
• Highly specific (>96%) for identifying invasive lesions, even in non-expert hands 2
• Helps determine appropriate management strategies based on predicted histology 3
• Assists in the "resect and discard" strategy for diminutive polyps, potentially reducing pathology costs 3, 4

Comparison to Other Classification Systems

While several other classification systems exist, the NICE classification is particularly valuable in Western practice:

• Kudo Pit Pattern Classification: Requires magnification colonoscopy with dye spray; classifies pits into 6 patterns (I, II, III-S, III-L, IV, V) 1

• Japanese NBI Expert Team (JNET) Classification: Further subdivides Type 2 into 2A (low-grade intramucosal neoplasia) and 2B (high-grade intramucosal neoplasia/superficial submucosal invasive cancer) 1

• Other Systems: Hiroshima, Sano, Showa, Jikei, and BASIC classifications are used mainly in Asian countries and are not commonly employed in the United States 1

Practical Implementation

For optimal use of the NICE classification:

• Carefully assess vessel pattern and surface pattern characteristics using NBI 1
• Type 3 lesions are highly specific (although not sensitive) for deep submucosal invasive cancer 1, 2
• Consider additional morphological features like ulceration, depression, and nodularity which can affect accuracy of identification 2

Pitfalls and Limitations

• Interobserver agreement can be modest, especially among non-expert endoscopists 1
• The sensitivity for detecting deep invasion is moderate (58.4%), though specificity is excellent (96.4%) 2
• Some studies suggest the modified Sano's classification may outperform NICE in differentiating neoplastic polyps and predicting endoscopic resectability 5
• Proper training is essential for accurate optical diagnosis using the NICE system 4, 6

The NICE classification provides a practical, validated approach to colorectal polyp assessment that can guide management decisions and potentially reduce unnecessary pathologic analysis of diminutive polyps 3, 4.