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Surgical Pathology Criteria

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Traditional Serrated Adenoma


  • Serrated polyp of the colon and rectum with generalized cytologic dysplasia

Alternate/Historical Names

  • Serrated adenoma
  • Serrated adenoma type II

Covered separately

Diagnostic Criteria

  • Prominent serration of glands
    • Usually columnar cells with mucin depleted eosinophilic cytoplasm
  • Cytologic low grade dysplasia throughout
    • Hyperchromatic elongate nuclei
    • Frequent nuclear stratification
  • Complex architecture
    • Ectopic crypt formation
      • Short, crypts oriented at right angles ot main crypt
        • Unlike normal crypts they do not reach to muscularis mucosae
      • Multiple adjacent crypts contribute to serrated appearance
        • In SSA and HP, serrations are predominantly formed by apical cytoplasm
    • Filiform variant with long thin surface projections
      • Complex villi with serrated surface
      • Frequent stromal edema producing bulbous ends
      • Lined by tall non-mucinous eosinophilic cytoplasm
      • Appears to be restricted to the left colon and rectum
  • Usually, but not always, pedunculated and left sided
  • May be associated with left sided carcinomas
    • Development of focal high grade dysplasia may represent an accelerated phase of carcinoma development
    • No clear association with sporadic MSI high carcinomas
  • Not typically a component of serrated adenomatous polyposis (hyperplastic polyposis)

Robert V Rouse MD
Amirkaveh Mojtahed MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting/last update: 1/31/10, 10/10/14

Supplemental studies


  • ANXA10 negative (Weiland)
  • 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 50-80% Minority (~0-10%)
    BRAF 20-40% 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, O’Brien 2006 and Weiland 2014)

Differential Diagnosis

Traditional Serrated Adenoma Sessile Serrated Polyp / Adenoma
Cytologic dysplasia throughout Cytologic dysplasia, if present, is a focal lesion
Multiple short crypts, right angled, not reaching the muscularis mucosae Basal dilation and flattening, boot or inverted T shaped, but overall, crypts are vertically arranged and span entire thickness of mucosa
Serration predominantly due to multiple adjacent ectopic crypts Serration predominantly due to exaggerated apical cytoplasm
Proliferation (Ki67) largely restricted to ectopic crypts Patches of proliferation can be seen at all levels
Predominantly polypoid and left sided Sessile and predominantly right sided


Traditional Serrated Adenoma Colorectal Tubular Adenoma
Serrated architecture Lacks prominent serration
Complex buds (ectopic crypts) all communicate with lumen Complex glands may not always communicate with surface
CK20 restricted to luminal surfaces CK20 staining random


Filiform Variant of Traditional Serrated Adenoma Villous Adenoma
Villi lined by complex serrations Villi lined by relatively uniform columnar cells
Frequent edematous bulbous ends on villi Villi typically pointed


Traditional Serrated Adenoma Hyperplastic Polyp
Cytologic dysplasia throughout Lacks cytologic dysplasia
Typically complex architecture Crypts are vertically arranged and not complex
Multiple ectopic crypt foci (short disoriented crypts not reaching the muscularis mucosae) Crypts each span from lumen to muscularis mucosae


  • Primarily occur in adults
    • Mean age 65 years, range 40-90
  • Should probably be counted as a tubular adenoma when determining followup colonoscopy intervals (see discussion of followup intervals for usual adenomas)


  • Bosman FT, Carneiro F, Hruban RH, Thiese ND (Eds). WHO Classifiication of Tumors of the Digestive System, IARC, Lyon 2010
  • Longacre TA, Fenoglio-Preiser CM. Mixed hyperplastic adenomatous polyps/serrated adenomas. A distinct form of colorectal neoplasia. Am J Surg Pathol. 1990 Jun;14(6):524-37.
  • East JE, Saunders BP, Jass JR. Sporadic and syndromic hyperplastic polyps and serrated adenomas of the colon: classification, molecular genetics, natural history, and clinical management. Gastroenterol Clin North Am. 2008 Mar;37(1):25-46
  • Snover DC, Jass JR, Fenoglio-Preiser C, Batts KP. Serrated polyps of the large intestine: a morphologic and molecular review of an evolving concept. Am J Clin Pathol. 2005 Sep;124(3):380-91.
  • Li SC, Burgart L. Histopathology of serrated adenoma, its variants, and differentiation from conventional adenomatous and hyperplastic polyps. Arch Pathol Lab Med. 2007 Mar;131(3):440-5.
  • Sandmeier D, Seelentag W, Bouzourene H. Serrated polyps of the colorectum: is sessile serrated adenoma distinguishable from hyperplastic polyp in a daily practice? Virchows Arch. 2007 Jun;450(6):613-8.
  • Sheridan TB, Fenton H, Lewin MR, Burkart AL, Iacobuzio-Donahue CA, Frankel WL, Montgomery E. Sessile serrated adenomas with low- and high-grade dysplasia and early carcinomas: an immunohistochemical study of serrated lesions "caught in the act". Am J Clin Pathol. 2006 Oct;126(4):564-71.
  • Goldstein NS. Small colonic microsatellite unstable adenocarcinomas and high-grade epithelial dysplasias in sessile serrated adenoma polypectomy specimens: a study of eight cases. Am J Clin Pathol. 2006 Jan;125(1):132-45.
  • Owens SR, Chiosea SI, Kuan SF. Selective expression of gastric mucin MUC6 in colonic sessile serrated adenoma but not in hyperplastic polyp aids in morphological diagnosis of serrated polyps. Mod Pathol. 2008 Jun;21(6):660-9.
  • Yantiss RK, Oh KY, Chen YT, Redston M, Odze RD. Filiform serrated adenomas: a clinicopathologic and immunophenotypic study of 18 cases. Am J Surg Pathol. 2007 Aug;31(8):1238-45.
  • Farris AB, Misdraji J, Srivastava A, Muzikansky A, Deshpande V, Lauwers GY, Mino-Kenudson M. Sessile serrated adenoma: challenging discrimination from other serrated colonic polyps. Am J Surg Pathol. 2008 Jan;32(1):30-5.
  • Torlakovic EE, Gomez JD, Driman DK, Parfitt JR, Wang C, Benerjee T, Snover DC. Sessile serrated adenoma (SSA) vs. traditional serrated adenoma (TSA). Am J Surg Pathol. 2008 Jan;32(1):21-9.
  • Makinen MJ Colorectal Serrated Adenocarcinoma. Histopathology 2007; 50, 131-150
  • O’Brien MJ, Yang S, Mack C, et al. Comparison of microsatellite instability, CpG Island methylation phenotype, BRAF and KRAS status in serrated polyps and traditional adenomas indicates separate pathways to distinct colorectal carcinoma end points. Am J Surg Pathol. 2006;30:1491–1501.
  • Wiland HO 4th, Shadrach B, Allende D, Carver P, Goldblum JR, Liu X, Patil DT, Rybicki LA, Pai RK. Morphologic and molecular characterization of traditional serrated adenomas of the distal colon and rectum. Am J Surg Pathol. 2014 Sep;38(9):1290-7.
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