Colon
Syndromes
Serrated polyposis


Topic Completed: 1 July 2016

Minor changes: 3 March 2021

Copyright: 2003-2021, PathologyOutlines.com, Inc.

PubMed Search: Serrated polyposis [title] colon tumor

Michael Feely, D.O.
Raul S. Gonzalez, M.D.
Page views in 2020: 969
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Cite this page: Feely M, Gonzalez RS. Serrated polyposis. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/colontumorserratedpolyposissx.html. Accessed August 2nd, 2021.
Definition / general
  • Polyposis syndrome defined by the development of numerous sessile serrated polyps in the colon
Essential features
  • WHO diagnostic criteria: (a) at least 5 serrated polyps proximal to the rectum, all ≥ 5 mm in size, with 2 or more of these being ≥ 10 mm; or (b) > 20 serrated polyps of any size, distributed throughout the colon, with at least 5 proximal to the rectum
  • Significantly increased risk for colorectal carcinoma and possibly extracolonic malignancies (Gut 2010;59:1094, Dis Colon Rectum 2011;54:164)
  • Family members also at increased risk for colorectal malignancies, suggesting an inherited component (Am J Gastroenterol 2012;107:770)
  • Likely represents a heterogeneous group of patients that includes several phenotypes of serrated polyposis
Terminology
  • Previously referred to as hyperplastic polyposis syndrome, although serrated polyposis is current preferred term by WHO
Sites
Pathophysiology
  • Likely consists of at least 2 groups: (type 1) patients with BRAF mutations and relatively few large right sided polyps and (type 2) patients with KRAS mutations and many small left sided polyps (J Pathol 2007;212:378)
  • Awaiting more definitive molecular genetic studies
Clinical features
  • Mean age at diagnosis is 55 years, with overall equal distribution in males and females
  • Type 1 patients (with BRAF mutations) typically female smokers (United European Gastroenterol J 2016;4:305)
  • Typically asymptomatic and encountered on screening colonoscopy, although larger polyps may bleed
  • Most cases appear de novo, although a few familial cases have been described
Treatment
  • Colonoscopy for polyp removal every 1 - 3 years, depending on polyps present
  • Colectomy with ileorectal anastomosis in cases of advanced lesions or those not amenable to colonoscopic management
  • Some recommend screening colonoscopy in first degree family members (Am J Gastroenterol 2012;107:770)
Microscopic (histologic) description
  • Lesions typically consist of sessile serrated adenomas / polyps that may have cytologic dysplasia
  • Hyperplastic polyps, typically of the microvesicular type, are also encountered and may be large
  • Conventional adenomas are occasionally present and may represent sessile serrated adenomas / polyps with cytologic dysplasia
Microscopic (histologic) images

Images hosted on other servers:

Sessile serrated
adenoma without
dysplasia (a) and with
low grade dysplasia (b)

Molecular / cytogenetics description
  • In addition to BRAF and KRAS mutations (as above), RNF43 has recently been implicated in sporadic and familial sessile serrated polyps (Gut 2017;66:1645)
Sample pathology report
  • Colon, total colectomy:
    • Colon with approximately two dozen sessile serrated lesions, some with focal cytologic dysplasia (see comment)
    • Negative for malignancy.
    • Sessile serrated lesion focally present at proximal resection margin; distal resection margin unremarkable.
    • Fourteen benign lymph nodes.
    • Comment: The findings are consistent with the patient's reported history of serrated polyposis. All grossly identifiable polyps were submitted for microscopy.
Differential diagnosis
Board review style question #1
Which of the following is true about serrated polyposis syndrome?

  1. It has been linked to MLH1 germline mutations
  2. Patients only develop sessile serrated adenomas
  3. Patients usually present with lower gastrointestinal bleeding
  4. There appear to exist 2 distinct subgroups
Board review style answer #1
D. There appear to exist 2 distinct subgroups

Comment Here

Reference: Serrated polyposis
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