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traditional serrated adenoma

Thursday 10 July 2008

traditional serrated polyp; TSA

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Definition: Traditional serrated adenoma (TSA) is a unique and uncommon type of true adenoma that exhibits low grade nuclear dysplasia similar to that seen for conventional adenoma, and also shows a serrated architecture similar to that seen for HP and SSA/P. Prominent cytoplasmic eosinophilia and a villous growth pattern are characteristic.

Images

- Traditional Serrated Adenoma: TSA’ T’opic crypt foci. Also: maturation down to Top + eosinophilic Tall cells droit de la de

In North America, TSAs are relatively uncommon, occur mainly in the left colon, and in some studies, have not been shown to have a strong association with hyperplastic polyp (HPP) or sessile polyp adenoma (SSA) precursor lesions.

Up to one-third of TSAs show a histologically identifiable non-dysplastic hyperplastic polyp (HPP) or sessile polyp adenoma (SSA) precursor lesion, particularly in lesions from the right colon.

The pathogenesis and risk of malignancy of traditional serrated adenomas (TSAs) are unclear.

The development of KRAS mutations and methylation of MGMT may herald the onset of an aggressive phenotype in the neoplastic progression of TSAs and also suggests that a fusion between the serrated pathway of carcinogenesis and the chromosomal instability pathway (MSI, MMR) may occur in some TSAs.

Microscopy

- traditional serrated adenoma (TSA)

  • TSAs, usually present on distal location, are dysplastic serrated polyps which lack SSA patterns and more closely resemble conventional adenoma with tubulovillous architecture.
  • Ectopic crypt formation, defined by the presence of crypts with bases not seated adjacent to the muscularis mucosae, is a feature that makes it possible to distinguish between TSAs and SSAs.
  • Columnar cells from the epithelium show eosinophilic cytoplasm, centrally placed elongated nuclei that are hyperchromatic and display pseudostratification.
  • There is no strong morphological evidence suggesting that SSAs are the precursor of TSAs, otherwise there are some histological and epidemiologic differences for keeping these lesions apart in different categories.
  • TSAs have been associated with distal location and MSS, CIMP-low CRCs with KRAS mutations.

In "traditional serrated adenomas", by contrast, the branching process is often incomplete so that the serrated contour is produced by rows of intra-epithelial micro-acini.

Additionally, the epithelium of "traditional serrated adenoma" is more overtly dysplastic, the crypts are back-to-back with little intervening lamina propria, and the architecture is frequently tubulovillous or villous.

Genetics

- Acquisition of WNT Pathway Gene Alterations Coincides With the Transition From Precursor Polyps to Traditional Serrated Adenomas. (30179900)

- KRAS mutations

  • The development of KRAS mutations and methylation of MGMT may herald the onset of an aggressive phenotype in the neoplastic progression of TSAs and also suggests that a fusion between the serrated pathway of carcinogenesis and the chromosomal instability pathway may occur in some TSAs.

See also

- serrated polyps (SPs)

  • dysplastic serrated polyps
    • traditional serrated polyp (TSA)
    • sessile serrated polyp (SSA/P)

- serrated adenomas (SAs)

- serrated polyposis

  • serrated polyposis syndrome

Open references

- Serrated polyposis syndrome: Molecular, pathological and clinical aspects
Carla Guarinos et al., 2012. Serrated polyposis syndrome: Molecular, pathological and clinical aspects. World J Gastroenterol 2012 May 28; 18(20): 2452-2461 - http://www.wjgnet.com/1007-9327/full/v18/i20/2452.htm

References

- Acquisition of WNT Pathway Gene Alterations Coincides With the Transition From Precursor Polyps to Traditional Serrated Adenomas. Hashimoto T, Ogawa R, Yoshida H, Taniguchi H, Kojima M, Saito Y, Sekine S. Am J Surg Pathol. 2018 Aug 31. doi : 10.1097/PAS.0000000000001149 PMID: 30179900

- KRAS mutations in traditional serrated adenomas (TSA) from Korea herald an aggressive phenotype. Kim KM, Lee EJ, Kim YH, Chang DK, Odze RD. Am J Surg Pathol. 2010 May;34(5):667-75. PMID: 20305537

- 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. PMID: 18162766

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