[582] MUC Expression in Hyperplastic and Serrated Colonic Polyps: Lack of Specificity of MUC6

JA Gibson, HP Hahn, RD Odze. Brigham and Women's Hospital, Boston, MA

Background: Previous studies have shown that hyperplastic (HP) and serrated polyps (SP) of the colon show variable degrees of gastric and intestinal-type MUC expression. One previously published study suggested that MUC6 expression, in particular, is specific for sessile serrated polyps (SSP) and, thus, can be used to distinguish these lesions from HP clinically (Owens, et al. Mod Pathol 2008;21:660-669). However, anecdotal data from our group suggests that MUC antibodies are not reliable in this differential diagnosis. Thus, the aim of this study was to systematically evaluate MUC expression in HP, SSP, and other SP and to determine the reliability of these antibodies in differentiating these polyp subgroups.
Design: Routinely processed specimens from 221 polyps (61 HP, 48 SSP, 51 SSP with dysplasia (SSP-D), 21 traditional serrated adenomas (TSA) and 40 conventional adenomas (CA)) were immunohistochemically stained with MUC1, MUC2, MUC5AC, and MUC6 and scored for extent (0-3), intensity (0-3) and crypt location (basal, superficial) of staining. The data was compared between the different polyp groups.
Results: MUC1, 2, and 5AC showed no significant differences in the location, extent, and intensity of staining between any of the polyp subgroups, including CAs. MUC6 expression was positive in 59%, 91%, 79%, 41%, and 43% of HP, SSP, SSP-D, TSA, and CA, respectively. Thus, MUC6 was not specific to SSP as reported previously. MUC6 staining was noted predominantly in the basal crypts. However, both the extent and intensity of MUC6 staining was significantly higher in SSP compared to HP (p value for extent: <0.001, intensity: 0.03). MUC6 expression was significantly decreased in TSA and CA compared to SSP either with or without dysplasia (p<0.0001 and p<0.02, respectively). For HP, no differences were noted in MUC6 expression between goblet cell, microvesicular and mucin depleted polyps.
Conclusions: Our MUC6 data supports the emerging theory that a subset of HP's represent a precursor to SSP. MUC6 is not specific for SSP and cannot be used reliably to distinguish this lesion from HP.
Category: Gastrointestinal

Tuesday, March 10, 2009 2:00 PM

Platform Session: Section B, Tuesday Afternoon