Protein-losing pseudomembranous colitis with cap polyposis-like features

Figure 4 Typical features of protein-losing colitis demonstrated by immunohistochemistry and special stains. A: Strong cytokeratin 20 expression (brown) by hyperplastic and attenuated (arrows) epithelial cells; B: Detection of rare CD3⁺ T-cells (brown, arrows) in the lamina propria and epithelium; C: Acid fuchsin orange G-stain (AFOG) stain demonstrating proteins (red) in the apical part of the denuded crypts; the granulation tissue and the pseudomembranes covering the surface, but not in the deeper parts of the mucosa; D, E: AFOG stain combined with a PAS reaction highlighting the presence of both proteins (red) and admixed mucus (pale pink, stars); E: Abundant pale pink mucus (star) but no significant proteins in the crypts lined by hyperplastic goblet cells.