title: Do serrated neoplasms of the small intestine represent a distinct entity? Pathological findings and molecular alterations in a series of 13 cases.
abstract: OBJECTIVE
  To characterize pathological, immunohistochemical and molecular features of small intestinal serrated neoplasms.
  
  
  RESULTS
  We report 13 serrated neoplasms located predominantly in the duodenum (median age, 71 years; male to female ratio, 7:6). The serrated adenomas demonstrated prominent serration, ectopic crypt formations and cytological features reminiscent of colorectal traditional serrated adenomas. Almost half the serrated adenomas demonstrated high-grade dysplasia or were associated with an adenocarcinoma. Immunohistochemical and molecular analysis showed an intestinal (CDX2-positive) phenotype in all tumours, abnormal β-catenin staining in three cases (23%), abnormal p53 expression in four cases (31%), focal loss of MGMT expression in one case (8%), KRAS mutation in five cases (38%) and CpG island methylator phenotype in six cases (50%). A diffuse pattern of Ki67 expression was present in eight adenomas (62%) and was associated with high-grade dysplasia (P = 0.02). No BRAF(V600E) mutation or loss of MLH1 expression was observed.
  
  
  CONCLUSIONS
  To our knowledge, this is the first series reporting serrated adenoma in the small intestine, a rare subtype of adenomas resembling traditional serrated adenoma with aggressive morphological features. The absence of the BRAF(V600E) mutation does not support a role for the serrated neoplasia pathway in the development of these lesions, as in colorectal serrated polyps.
authors.affiliation: Envoi Pathology, Brisbane, Qld, Australia; School of Medicine, University of Queensland, Brisbane, Qld, Australia; Genetic Epidemiology Laboratory, Department of Pathology, The University of Melbourne, Carlton, Vic., Australia.
authors.forename: Christophe
authors.initials: C
authors.lastname: Rosty
authors.forename: Catherine
authors.initials: C
authors.lastname: Campbell
authors.forename: Mark
authors.initials: M
authors.lastname: Clendenning
authors.forename: Mark
authors.initials: M
authors.lastname: Bettington
authors.forename: Daniel D
authors.initials: DD
authors.lastname: Buchanan
authors.forename: Ian S
authors.initials: IS
authors.lastname: Brown
mesh_terms: D000230:Adenocarcinoma / Q000235:genetics* / Q000473:pathology*; D000236:Adenoma / Q000235:genetics* / Q000473:pathology*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism; D004252:DNA Mutational Analysis; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D007414:Intestinal Neoplasms / Q000235:genetics* / Q000473:pathology*; D007421:Intestine, Small / Q000473:pathology; D008297:Male; D008875:Middle Aged
chemical_list: D014408:Biomarkers, Tumor
keywords: BRAF; CIMP; KRAS; serrated adenocarcinoma; serrated adenoma; small intestine; traditional serrated adenoma