Histopathology of general inflammatory markers
Formalin-fixed samples were processed with standard haematoxylin and eosin (H&E) staining and immunohistochemistry (IHC). A structured, manual histopathological assessment congruent with current CRS diagnostic criteria18 was performed for each H&E-stained section by an anatomical pathologist (PE) in a blinded manner. Overall degree of inflammation (defined by extent of general inflammatory cell infiltrate, oedema and tissue distortion), sub-epithelial oedema, fibrosis, basement membrane thickening, hyperplastic papillary change, mucosal ulceration, squamous metaplasia, and tissue neutrophil infiltrate per HPF (400x) were each scored according to subcategories.