The alphabet soup of polyp optical diagnosis

endoscopy2023-10-07

Maria Simona Badiu, Adrian Săftoiu

Colorectal Cancer (CRC) > a significant public health issue > the 2nd leading cause of cancer-related mortality worldwide > 70%-90% have adenomatous polyps as precursors (prevention through screening colonoscopy) Classification of Polyps > Currently, there are 3 main categories defined

hyperplastic polyps (benign)
adenomatous polyps (premalignant)
sessile serrated polyps account for approximately 15-30% of colorectal cancer cases (Figure 1)

> Size is essential > ~ 90% of resected polyps are < 10 mm, with 70-80% being diminutive (<5 mm)

only ~ 0.5% of diminutive polyps (< 5mm), and 1.5% of small ones (6-9 mm), are histologically advanced
important strategies
- "resect & discard" versus "diagnose & leave-in"
- increasing withdrawal time (6 min > 9 min)
- virtual chromoendoscopy (sequential red-green-blue illumination, modifying the conventional white light source with special filters (NBI-Narrow Band Imaging) or special software (FICE; I-scan)
- NICE (NBI International Colorectal Endoscopic) or J-NET (Japan NBI Expert Team) classification

> NICE classification, based on color, vessel appearance, and polyp surface

good accuracy for differentiating between hyperplastic (type 1) and adenomatous (type 2) polyps
low accuracy in identifying sessile serrated polyps, often considered hyperplastic polyps

> WASP classification introduced in 2016 by the Workgroup Serrated Polyps and Polyposis (WASP)

combines the NICE classification and criteria proposed by Hazewinkel et al.
- irregular surface - cloud-like appearance
- indistinct borders
- irregular shape
- dark spots inside the crypts
the objective of the WASP classification
- to differentially diagnose between hyperplastic, conventional adenomatous, and sessile serrated polyps < 10 mm, in a step-wise evaluation (Figure 2)
  - Step 1 - applying the NICE classification criteria and categorizing into one of the 2 nonspecific sessile serrated polyps (NICE 1 versus NICE 2)
  - Step 2 - applying specific criteria for sessile serrated polyps - the presence of at least 2 of these criteria is sufficient for diagnosis

> Good to know

modified SANO classification
- includes sessile serrated polyps (SSP) / sessile serrated adenomas (SSA) - MS type Iio
- recent comparative studies have shown the superiority of the MS score in identifying SSA/SSP compared to WASP+NICE and WASP+J-NET, respectively
confocal laser endomicroscopy (CLE) > allows "optical biopsy," possibly playing a role in diagnosing SSP/SSA
serrated polyposis syndrome > 3-5 times higher risk of developing CRC compared to the general population > follow-up colonoscopy every 3 years (according to ESGE recommendations)