Surgical Pathology Criteria

Sessile Serrated Polyp / Adenoma

Differential Diagnosis

Hyperplastic Polyp Sessile Serrated Polyp / Adenoma
≥90% of bases of crypts straight, regular, narrow, frequently pointed, no dilated flattened bases 1 to 3 crypts required with basal dilation and flattening, bases boot or inverted T shaped, <90% of bases are narrow
Proliferative zone reliably restricted to base Bases contain mature mucous cells
Serrations and CK20+ maturation limited to luminal 2/3 of crypt Serrations and CK20+ patches of maturation can be seen at all levels
Predominantly left sided and small Predominantly right sided and frequently ≥1 cm
Polyps with mixed or intermediate features are designated indeterminate (e.g. between 50-90% narrow crypts and/or <3 flat crypt bases)

 

Traditional Serrated Adenoma Sessile Serrated Polyp / Adenoma
Cytologic dysplasia throughout Cytologic dysplasia, if present, is a focal lesion
Multiple short crypts, right angled, not reaching the muscularis mucosae Basal dilation and flattening, boot or inverted T shaped, but overall, crypts are vertically arranged and span entire thickness of mucosa
Serration predominantly due to multiple adjacent ectopic crypts Serration predominantly due to exaggerated apical cytoplasm
Proliferation (Ki67) largely restricted to ectopic crypts Patches of proliferation can be seen at all levels
Predominantly polypoid and left sided Sessile and predominantly right sided

 

Usual Colorectal Adenoma Sessile Serrated Polyp / Adenoma
Cytologic dysplasia throughout Cytologic dysplasia, if present, is a focal lesion
Typically complex architecture Basal dilation and flattening, boot or inverted T shaped, but overall, crypts are vertically arranged and not complex
Lacks serrations Prominent serrations

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