Serrated lesions of the appendix in serrated polyposis patients

Patients with serrated polyposis develop multiple serrated polyps throughout the large bowel: hyperplastic polyps (HP), sessile serrated adenomas (SSA) and traditional serrated adenomas (TSA). The frequency and the characteristics of serrated lesions of the appendix have not been reported in serrated polyposis patients. We conducted a retrospective study of 34 serrated polyposis patients who underwent a total or right hemicolectomy for adenocarcinoma or polyp burden. An appendiceal serrated lesion was identified in 23 (68%): 13 SSAs, three SSAs with dysplasia, four HPs and three TSAs. The BRAF(V600E) mutation was present in four polyps, all of SSA subtype (one with dysplasia). KRAS mutations were identified in 11 polyps (48%), in more than half of SSAs and of TSAs, and in none of the four HPs. None of the polyps displayed high levels of CpG island methylator phenotype (CIMP). There was no methylation in the promoter of the MLH1, p16 or MGMT gene. Serrated lesions of the appendix are frequently found in serrated polyposis patients and are most commonly of SSA-type morphology, frequently associated with KRAS mutation. It is unclear if appendiceal serrated polyps are a feature of serrated polyposis or a lesion frequently identified in association with a proximal colonic adenocarcinoma.