Neutrophil infiltrates and eosinophil aggregates in chronic rhinosinusitis with nasal polyps and EGPA

Introduction/objectives The histopathological study of inflammatory cells and their tendency to form aggregates in chronic rhinosinusitis with nasal polyps (CRSwNP) has shown promising results in determining the pathogenesis and predicting clinical outcome. Bilateral nasal polyps also occur in over 70% of patients with eosinophilic granulomatosis with polyangiitis (EGPA). The study aim was to investigate neutrophil infiltrates and eosinophil aggregates in CRSwNP and EGPA tissues of Caucasian patients. Method A histopathological study was performed on surgical specimens of nasal polyps from 144 adults (15 with allergic fungal rhinosinusitis; 19 with nonsteroidal anti-inflammatory drugs-exacerbated respiratory disease (NERD); 16 with intrinsic asthma; 21 with extrinsic asthma; 21 with allergy; 22 with eosinophil CRSwNP (ECRSwNP); 17 with non-ECRSwNP; 13 with EGPA). Results Focusing on the presence of tissue eosinophil aggregates, NERD and ECRSwNP were the sub-cohorts with the highest rate. Neutrophil infiltrate rate was significantly higher in EGPA sub-cohort than in all CRSwNP sub-cohorts apart from non-ECRSwNP. Conclusions Structured histopathology is increasingly identifying the different histotypes of CRSwNP. This analysis can be used to better understand CRSwNP endotypes and develop targeted therapies. The response to therapy and therefore control of CRSwNP relapses definitely depends on our ability to act on the underlying inflammatory pattern.