Interobserver Agreement in rhe Diagnosis of Serrated Polyps and Identification of Prolapse Hyperplastic Polyps as Histologic Mimics of Sessile Serrated Adenomas
RK Pai, J Hart, A Noffsinger. University of Chicago, Chicago, IL
Background: Sessile serrated adenomas (SSAs) can be extremely difficult to distinguish from hyperplastic polyps (HPs), particularly the microvesicular HP. In one recent study the interobserver agreement in the diagnosis of serrated lesions was moderate with a kappa score of 0.58. In that study only sessile serrated adenomas larger than 5 mm and those that were well-oriented were included. In this study we set out to determine the interobserver agreement in serrated lesions independent of polyp size and orientation. Moreover, our aim was to identify any unique characteristics of those polyps that presented the most difficulty in the histologic diagnosis.
Design: 172 SSAs, 13 SSAs with dysplasia, and 89 hyperplastic polyps were identified from our surgical pathology database. Two GI pathologists independently reviewed these polyps blinded to location. After this independent review, a consensus conference was convened to resolve any differences between the two pathologists or with the sign-out diagnoses.
Results: The interobserver agreement as measured by the Cohen's kappa score was 0.63 (moderate). At the consensus conference, 15 polyps originally diagnosed as SSAs were designated as hyperplastic polyps. Of these, 9 were located in the left colon and had features of mucosal prolapse. 36 left sided SSAs were subsequently reviewed for evidence of prolapse. 18/36 (50%) had features of prolapse in addition to features diagnostic of an SSA.
Conclusions: The diagnosis of serrated lesions is quite difficult as there is considerable overlap between hyperplastic polyps and SSAs. In this study, we show that the interobserver agreement in the diagnosis of serrated lesions regardless of size and orientation is moderate with a Cohen's kappa score of 0.63. We also identify prolapsed hyperplastic polyps as histologic mimics of SSAs. Mucosal prolapse has been known to cause architectural abnormalities such as crypt branching and dilation. However, 50% of SSAs in the left colon can also show features of prolapse. Thus when diagnosing a SSA in the left colon, one must be sure to exclude the possibility of a hyperplastic polyp with superimposed features of mucosal prolapse.
Wednesday, March 11, 2009 9:30 AM
Poster Session V # 78, Wednesday Morning