Traditional Serrated Adenoma of the Appendix

Definition

Serrated appendiceal polyp with generalized cytologic dysplasia

Diagnostic Criteria

Histologic features of colorectal TSA

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

Budding and branching of glands similar to usual tubular adenomas

One study found 4 of 10 appendiceal TSA to have associated invasive carcinoma (Rubio 2004)
Unequivocal diagnosis of TSA should be made only if the appendix has been entirely sectioned and the margins of resection are clear
No relationship to pseudomyxoma peritonei has been demonstrated

Teri A Longacre MD
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting/updates : 10/7/10

Supplemental studies

No studies currently useful for diagnosis, but following may shed some light on the nature of serrated lesions of the appendix (based on Yantiss 2007)

CpG island DNA hypermethylation is evident in about half of appendiceal hyperplastic polyps, sessile serrated adenomas, traditional serrated adenomas, and SSA with dysplastic foci (SSAD)
MLH1 staining is lost in about 50% of all four
- Nevertheless, MSI is extremely rare in all four
MGMT staining is lost in about 50% of HP, SSA and TSA, and 100% of SSAD
BRAF is mutated in 20-25% of HP, TSA and SSAD and 47% of SSA
KRAS is mutated in 20-40% of all four
Only 1 of 4 carcinomas associated with SSA was MSI high
No clear pattern of progression to support a serrated neoplasia pathway as in the colorectum

Differential Diagnosis

Appendiceal traditional serrated adenoma should be distinguished from appendiceal sessile serrated adenoma using the same features as in the colorectum

Appendiceal Traditional Serrated Adenoma Appendiceal Mucinous Adenoma

Prominent glandular serration No serrated/hyperplastic appearance

Typically complex architecture Flat with areas of short villi

Distinction may be difficult in lesions compressed by mucin

Appendiceal traditional serrated adenoma should be distinguished from appendiceal sessile serrated adenoma using the same features as in the colorectum

Appendiceal Traditional Serrated Adenoma	Appendiceal Sessile Serrated Polyp/Adenoma
Cytologic dysplasia throughout	Cytologic dysplasia, if present, is a focal lesion
Typically complex architecture	Minor architectural disturbances but overall, crypts are vertically arranged and not complex

Significance of the distinction in the appendix is not clear
Both are benign if completely excised and completely sectioned

Lists

Appendiceal Epithelial Neoplasms and Proliferations

Clinical / Descriptive Terms

Bibliography

Pai RK, Longacre TA. Appendiceal mucinous tumors and pseudomyxoma peritonei: histologic features, diagnostic problems, and proposed classification. Adv Anat Pathol. 2005 Nov;12(6):291-311.
Yantiss RK, Panczykowski A, Misdraji J, Hahn HP, Odze RD, Rennert H, Chen YT. A comprehensive study of nondysplastic and dysplastic serrated polyps of the vermiform appendix. Am J Surg Pathol. 2007 Nov;31(11):1742-53.
Renshaw AA, Kish R, Gould EW. Sessile serrated adenoma is associated with acute appendicitis in patients 30 years or older. Am J Clin Pathol. 2006 Dec;126(6):875-7.
Rubio CA. Serrated adenomas of the appendix. J Clin Pathol. 2004 Sep;57(9):946-9.

Printed from Surgical Pathology Criteria: http://surgpathcriteria.stanford.edu/


© 2009 Stanford University School of Medicine

Traditional Serrated Adenoma of the Appendix