Immunohistochemistry of mast cells, 5-HT, and IL-6 (magnification 60×). A-F. FFPE GI mucosa block sectioned and immunostained for mast cells, 5-HT, and IL-6. A-B. Increased mast cell counts per HPF in non-inflammatory biopsies compared to inflammatory biopsies. C-D. No significant difference between phenotypes in 5-HT immunoreactivity. E-F. Increased IL-6 immunoreactivity of inflammatory biopsies compared to non-inflammatory biopsies.