Hyperplastic Polyp of the Colon and Rectum
Supplemental Studies
Immunohistology
- Staining is not generally needed for the diagnosis
- MUC6 completely negative
- MLH1 stain typically positive
| |
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
- Genetic studies not generally used for diagnosis
- MSI normal or low
- KRAS (microvesicular polyps) or BRAF (goblet cell rich polyps) mutations are frequently present
- This is not generally needed for the diagnosis
- CpG island DNA hypermethylation may be present
- Involving MGMT (26%) and MLH1 (40%) (in microvesicular type HP)
- Infrequent APC and p53 mutations
