Appendix
Benign tumors
Serrated polyp
Authors: Michael Feely, D.O., Raul S. Gonzalez, M.D.
Last author update: 13 April 2021
Last staff update: 18 June 2024
Copyright: 2003-2024, PathologyOutlines.com, Inc.
PubMed Search: Appendix serrated polyp
Table of Contents
Definition / general | Essential features | Terminology | Clinical features | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Molecular / cytogenetics description | Sample pathology report | Differential diagnosis | Additional references | Board review style question #1 | Board review style answer #1Cite this page: Feely M, Gonzalez RS. Serrated polyp. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/appendixserratedpolyps.html. Accessed November 27th, 2024.
Definition / general
- Benign serrated lesion of the appendix
Essential features
- Benign appendix polyp that may show cytologic atypia / dysplasia
- Harbors KRAS mutations
Terminology
- Serrated polyp is currently preferred terminology over sessile serrated adenoma / polyp, as appendiceal lesions appear to have different mutations than similar lesions in the colon (Am J Surg Pathol 2016;40:14)
- Presence or absence of dysplasia should be noted
Clinical features
- Typically an incidental finding at the time of appendectomy
Gross images
Contributed by Raul S. Gonzalez, M.D.
Small polyp
Ill defined polyp
Microscopic (histologic) description
- Localized serrated epithelial lesion within the luminal appendix, with retention of the muscularis mucosae
- Often circumferential
- Typically minimal to no nuclear atypia, though visible cytologic dysplasia (low grade or high grade) may sometimes be present
Microscopic (histologic) images
Contributed by Michael Feely, D.O.
Serrated polyp of appendix
Molecular / cytogenetics description
- Regularly harbor KRAS mutations; BRAF alterations are rare (Hum Pathol 2014;45:227)
- May lose MLH1 by immunohistochemistry but high frequency microsatellite instability not a feature (Am J Surg Pathol 2007;31:1742)
Sample pathology report
- Appendix, appendectomy:
- Serrated polyp with cytologic low grade dysplasia
- Negative for malignancy.
- Margin of resection negative for serrated polyp.
- Background acute appendicitis.
Differential diagnosis
- Appendiceal mucinous neoplasms:
- May demonstrate serrated features but will be associated with loss of the underlying muscularis mucosae
Additional references
Board review style question #1
Serrated polyp of the appendix differs from sessile serrated polyp / adenoma of the colon in what way?
- It favors KRAS mutation over BRAF mutation
- It has a higher incidence
- It never shows cytologic atypia
- It only occurs in patients with Lynch syndrome
- It rarely loses MLH1 by immunohistochemistry
Board review style answer #1
