Hyperplastic Polyp / Mucosal Hyperplasia of the Appendix
Supplemental Studies
No studies currently useful for diagnosis, but following may shed some light on the nature of serrated lesions of the appendix (based on Yantiss 2007)
CpG island DNA hypermethylation is evident in about half of appendiceal hyperplastic polyps, sessile serrated adenomas, traditional serrated adenomas, and SSA with dysplastic foci (SSAD)
MLH1 staining is lost in about 50% of all four
Nevertheless, MSI is extremely rare in all four
MGMT staining is lost in about 50% of HP, SSA and TSA, and 100% of SSAD
BRAF is mutated in 20-25% of HP, TSA and SSAD and 47% of SSA
KRAS is mutated in 20-40% of all four
Only 1 of 4 carcinomas associated with SSA was MSI high
No clear pattern of progression to support a serrated neoplasia pathway as in the colorectum
