2.5 Histological evaluation
Samples of nasal polyps were obtained from each participant during surgery, and which were treated with fixation and embedded in paraffin. Then, all of samples were sliced up sections and stained with hematoxylin and eosin, which were evaluated by two independent observers under the light microscope (Leica DM4B, Wetzlar, Germany). Five fields with densest inflammatory cells infiltration in the subepithelial layer were chosen at 100×magnificantion in each sample. Afterwards the whole inflammatory cells and eosinophils were observed at 400×magnificantion (high power field, HPF), and counted in the focal area. The amount of eosinophils and whole inflammatory cells were recorded in every focal area under HPF, and the proportion of eosinophils accounted for the whole inflammatory cells was calculated.