Traditional Serrated Adenoma
Supplemental Studies
Immunohistology
- MUC6 completely negative
- (Based on one report so far by Owens 2008)
- MLH1 staining may be negative but microsatellite instability is not present
| |
Ki67 |
CK20 |
| Normal mucosa |
Limited to basal ¼ |
Limited to surface |
| Hyperplastic polyp |
Expanded to basal 1/3-1/2 |
Expanded to luminal 1/2-2/3 |
| SSA |
Patches of staining at all levels |
Patches of staining at all levels |
| TSA |
Mainly localized to ectopic crypts |
Irregular staining of luminal surface |
| Usual adenoma |
High overall |
Random |
(based on Torlakovic 2008)
Genetic analysis
- Genotype is not useful for diagnosis but supportive of separate pathways for TSA and SSA
| |
Traditional Serrated Adenoma |
Sessile Serrated Polyp / Adenoma |
| KRAS |
Majority (~80%) |
Minority (~0-10%) |
| BRAF |
Minority (~20%) |
Majority (~75%) |
| p53 |
Infrequent |
Infrequent |
| APC |
Infrequent |
Infrequent |
| MSI |
Can lead to MSI-L or MSS Serrated adenocarcinoma (SAca) |
Can lead to MSI-H or L SAca |
| CpG island methylator phenotype (CIMP) |
Primarily MGMT involvement in SAca |
Primarily MLH1 involvement in SAca |
(based on Makinen 2007 and O’Brien 2006)
