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Critical Appraisal of the Diagnosis of the Sessile Serrated Adenoma

Bettington, Mark FRCPA*,†,‡; Walker, Neal FRCPA, MD†,‡; Rosty, Christophe FRCPA, PhD†,‡,§; Brown, Ian FRCPA‡,∥; Clouston, Andrew FRCPA, PhD†,‡,∥; Wockner, Leesa PhD; Whitehall, Vicki PhD*,†,#; Leggett, Barbara FRACP, MD*,†,**

American Journal of Surgical Pathology: February 2014 - Volume 38 - Issue 2 - p 158–166
doi: 10.1097/PAS.0000000000000103
Original Articles

The sessile serrated adenoma (SSA) is a relatively recently described polyp that can present diagnostic difficulties for the practicing pathologist. The frequency of SSA diagnoses varies dramatically in the reported literature. In addition, the histologic interface between the microvesicular hyperplastic polyp (MVHP) and the SSA continues to be a diagnostic problem. The trend in recent years has been toward a lower threshold for SSA diagnosis. Herein, we have performed a cross-sectional study of 6340 colorectal polyps received at a high-volume community-based pathology practice over a 3-month period. After central review, with strict application of the diagnostic criteria outlined in the 2010 edition of the World Health Organization Classification of Tumours of the Digestive Tract, we found that SSAs represented 12.1% of all polyps. In addition, we developed novel diagnostic subcategories in an attempt to determine the most appropriate cutoff for the interface between the MVHP and the SSA. We found that serrated polyps (MVHPs or SSAs) with any SSA-like crypts had clinical features more in common with the SSA than the MVHP and that this diagnostic cutoff showed good reproducibility between pathologists. This supports the position of a recent consensus publication proposing that polyps with as few as 1 SSA-type crypt should be diagnosed as an SSA. Applying these criteria to our cohort yields an overall SSA rate of 14.7%. In summary, we believe that SSAs continue to be underdiagnosed in pathologic practice and that this may result in inadequate surveillance and thus contribute to interval colorectal carcinomas.

*The Conjoint Gastroenterology Laboratory

§Cancer and Population Studies Group

The Statistics Unit, QIMR Berghofer Medical Research Institute

School of Medicine, The University of Queensland

Envoi Specialist Pathologists

Departments of Anatomical Pathology

#Chemical Pathology, Central Laboratory, Pathology Queensland

**The Royal Brisbane and Women’s Hospital, Brisbane, QLD, Australia

Conflicts of Interest and Source of Funding: M.B. received PhD scholarship funding from Cancer Council Queensland. The authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article.

Correspondence: Mark Bettington, FRCPA, The Conjoint Gastroenterology Laboratory, Level 7, CBCRC, QIMR Berghofer Medical Research Institute, 300 Herston Road, Herston, Brisbane, QLD 4006, Australia (e-mail: mark.bettington@qimr.edu.au).

© 2014 by Lippincott Williams & Wilkins.