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CLASSIFICATION
Classification
WHO 2019 serrated lesion histology
WHO 5th edition (2019) histological subtypes of colorectal serrated lesions. Common pathology language linked to WASP and SPS.
Classification overview
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Non-neoplastic
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HP · Hyperplastic polyp
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Neoplastic
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SSL · Sessile serrated lesion (no dysplasia)
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SSL-D · SSL with dysplasia
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TSA · Traditional serrated adenoma
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Other
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Unclassified · Unclassified serrated lesion
Non-neoplastic
HP
Hyperplastic polyp
Definition
Serrated crypts without architectural distortion of crypt bases; microvesicular or goblet-cell-rich hyperplastic mucosa
Dysplasia
None
Endoscopy
Often small rectosigmoid lesions; WASP Type 1 correlates
Neoplastic
SSL
Sessile serrated lesion (no dysplasia)
Definition
Serrated architecture with crypt distortion (dilated, branched, or horizontal crypt bases); no cytologic dysplasia
Terminology
Replaces sessile serrated adenoma/polyp (SSA/P)
Endoscopy
Often flat, mucus cap; WASP Type 2 (SSL) correlates
Note: Precursor of the serrated pathway. Management depends on size, margins, and dysplasia.
SSL-D
SSL with dysplasia
Definition
SSL architecture plus conventional adenomatous (low- or high-grade) dysplasia
Clinical
Higher progression risk than SSL without dysplasia
TSA
Traditional serrated adenoma
Definition
Serrated lesion with ectopic crypt foci and often eosinophilic cytoplasm; may show cytologic dysplasia
Endoscopy
Often protuberant; WASP Type 3 (TSA) correlates
Other
Unclassified
Unclassified serrated lesion
Definition
Serrated lesion that does not meet criteria for HP, SSL, SSL with dysplasia, or TSA
Clinical
Expert review or reclassification may be needed
WHO 2019, Original
More reference figures
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Reference
Original article
WHO Classification of Tumours: Digestive System Tumours, 5th ed, 2019
Review
Nagtegaal JD et al. Histopathology 2020
Related tools
WASP classification (HP / SSL / adenoma)
WASP endoscopic classification
CLASSIFICATION
WASP
→
Vienna classification (GI epithelial neoplasia)
Vienna classification
CLASSIFICATION
Vienna
→
SPS diagnostic criteria (serrated polyposis syndrome)
SPS diagnostic criteria
CLASSIFICATION
SPS
→
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Decision support only. Follow current guidelines and local protocols. Classification definitions and terminology follow the original publication language.