Traditional Serrated Adenoma
Differential Diagnosis
| 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 |
| Traditional Serrated Adenoma |
Colorectal Tubular Adenoma |
| Serrated architecture |
Lacks prominent serration |
| Complex buds (ectopic crypts) all communicate with lumen |
Complex glands may not always communicate with surface |
| CK20 restricted to luminal surfaces |
CK20 staining random |
| Traditional Serrated Adenoma |
Hyperplastic Polyp |
| Cytologic dysplasia throughout |
Lacks cytologic dysplasia |
| Typically complex architecture |
Crypts are vertically arranged and not complex |
| Multiple ectopic crypt foci (short disoriented crypts not reaching the muscularis mucosae) |
Crypts each span from lumen to muscularis mucosae |
