Serrated lesions of the appendix: do they differ from their colorectal counterparts?

BACKGROUND/AIMS The aim of this study is, therefore, to classify appendiceal serrated polyps in a large case series with respect to the recent World Health Organization classification using diagnostic criteria provided for colorectal serrated polyps. MATERIALS AND METHODS A total of 960 appendix specimens diagnosed between 2005 and 2010 were reviewed retrospectively, and cases presenting with a polyp with serrated morphology were classified with reference to the recent World Health Organization criteria. Histologic criteria comprised architectural features of the crypts, including serration, branching, basal dilatation, inverted T- or L-shaped crypts together with cytologic features comprising a mucin pattern, dysplasia, in terms of pseudostratification and nuclear atypia, mitoses in the upper crypts, and cytoplasmic eosinophilia. RESULTS A total of 71 cases (7.39%) were diagnosed as serrated polyps, including 36 (50.7%) hyperplastic polyps, 33 (46.48%) sessile serrated adenoma/polyps, and 2 (2.81%) traditional serrated adenomas. There were 32 males and 39 females with an age range of 2 to 82 years. Histology revealed that the majority of both hyperplastic polyps (63.9%) and sessile serrated adenomas/polyps (74.3%) involved the entire appendiceal circumference. Basal dilatation (94.3%), basal serration (94.3%), T-/L-shaped crypts (94.3%), and ectopic crypts (68.6%) were significantly more commonly observed in sessile serrated adenomas/polyps compared to hyperplastic polyps. Dysplasia was observed in 31.4% of sessile serrated adenomas/polyps, while hyperplastic polyps did not show dysplasia. CONCLUSION The results of the present study suggest that appendiceal serrated polyps, despite bearing many similarities with their colorectal counterparts, may have some special features due to the anatomic uniqueness of the organ itself and also the polyps arising from its mucosal lining.