Histology Matrix • WHO 2019 Serrated Classification
Histological Category
Select the lesion type from the pathology report to visualize the WHO serrated clinical profile.
Guidelines & Evidence
Clinical Details
Section 1
When to Use
When to Use
Histopathological diagnosis of colorectal serrated polyps
To guide the surveillance intervals after colonoscopy based on malignant potential
Standardizing pathological terminology following the WHO 5th Edition (2019) update
The 'Serrated Pathway'
At least 15–30% of colorectal cancers arise from serrated lesions rather than traditional adenomas. They are characterized by BRAF mutations and CpG island methylator phenotype (CIMP).
Section 2
Formula & Logic
The 3 Primary Types
01
Hyperplastic Polyp (HP): Simple serration limited to the upper half of the crypts. Common in the distal colon.
02
Sessile Serrated Lesion (SSL): Serration extending to the crypt base + Crypt distortion (horizontal growth).
03
Traditional Serrated Adenoma (TSA): Often pedunculated; Ectopic crypt formation (ECF); Characteristic eosinophilic cytoplasm.
The SSL Diagnostic Criteria
The 2019 WHO update simplified SSL diagnosis: Presence of at least ONE unequivocally distorted/dilated/branched crypt is sufficient for the diagnosis.
Cancer Risk Profile
HP
Negligible (unless massive/proximal)
SSL
High (Precursor to MSI-H/CIMP cancer)
TSA
High (Precursor to MSS/CIMP-low cancer)
Section 3
Pearls/Pitfalls
The "Invisible" SSL
SSLs are notoriously difficult to see during white-light colonoscopy. They are often flat (Paris 0-IIb), pale, and covered by a "mucus cap." Use of NBI or chromoendoscopy is highly recommended to visualize the "Rim of debris" that suggests an SSL.
SSL with Dysplasia
When an SSL develops cytological dysplasia (SSL-D), it is considered a very late-stage precursor. These lesions have an extremely fast progression rate to invasive cancer and must be completely resected with margin confirmation.
Clinical Pearls
Proximal serrated polyps > 10 mm are almost always SSLs until proven otherwise
Serrated Polyposis Syndrome (SPS) is diagnosed if > 5 serrated lesions are found proximal to the rectum (with at least two > 10 mm)
Serrated lesions in the right colon carry significantly higher risk than distal hyperplastic polyps
Section 4
Next Steps
USMSTF Surveillance intervals
01
SSL < 10 mm: 5–10 years.
02
SSL ≥ 10 mm or SSL with Dysplasia: 3 years.
03
Large HP (Proximal, > 10mm): 3–5 years.
Complementary Scoring
Paris Classification (Morphology)
JNET Classification (Vessels)
ADR (Adenoma Detection Rate) Benchmarks
Section 5
Evidence Appraisal
The WHO 5th Edition
Digestive System Tumours (5th Ed).
WHO Classification of Tumours Editorial Board. • IARC Press, Lyon. 2019;The current global authority on digestive pathology.
