The importance of MUC6 immunohistochemistry staining in the histopathologic examination of Crohn's disease: can we enhance our diagnostic power?

Abstract

Crohn's disease (CD) is a chronic inflammatory bowel disease characterized by transmural inflammation and histopathologic variability, making diagnosis challenging. Pseudopyloric metaplasia (PPM) is a key histological feature of chronicity in CD. However, its identification on hematoxylin & eosin (H&E)-stained slides is subject to interobserver variability. MUC6 immunohistochemistry (IHC) has been suggested as a useful marker for pyloric glands. This study aims to evaluate the diagnostic utility of MUC6 staining in detecting PPM and to assess interobserver agreement compared to H&E staining. In this retrospective study, 38 terminal ileum biopsies from CD patients were analyzed. H&E-stained and MUC6-stained slides were evaluated independently by four pathologists for the presence and gland count of PPM. Intraobserver and interobserver agreements were assessed using Intraclass Correlation Coefficient (ICC). The mean PPM count was significantly higher with MUC6 staining than by H&E alone. Intraobserver agreement between H&E and MUC6 staining was “moderate” (ICC = 0.577, 0.734, 0.738) for three pathologists and “poor” (ICC = 0.439) for one. Interobserver agreement was classified as “good” for H&E slides (ICC = 0.849) and “excellent” for MUC6-stained slides (ICC = 0.993). PPM is an important finding that is not specific for CD but indicates chronic mucosal damage in the gastrointestinal tract. In our study, MUC6 IHC staining in CD improved the detection of PPM and increased interobserver agreement in the detection of PPM. The increase in the number of detectable metaplastic glands in all observers demonstrates the potential of MUC6 staining as a reliable marker. MUC6 IHC may provide a more standardized and objective evaluation, reducing diagnostic variability.