A classification of chronic rhinosinusitis with nasal polyps based on structured histopathology.

AIMS: In chronic rhinosinusitis with nasal polyps (CRSwNP), tools based on objective evidence, such as histopathology, are needed to assist clinical decision-making. The main aim of this exploratory investigation was to determine whether structured histopathology could be used to classify CRSwNP in homogeneous histological clusters.

METHODS AND

RESULTS

A cohort of 135 CRSwNP patients was assessed, on the basis of clinicopathological features: allergic fungal rhinosinusitis (17 patients); non-steroidal anti-inflammatory drug-exacerbated respiratory disease (19 patients); intrinsic asthma (18 patients); extrinsic asthma (21 patients); allergy (21 patients); histologically eosinophilic (22 patients); and histologically non-eosinophilic (17 patients). For structured histopathology, we considered: the degree of inflammation; eosinophil count; eosinophil aggregates; neutrophil infiltration; goblet cell hyperplasia; basement membrane thickening; fibrosis; hyperplastic/papillary changes; squamous metaplasia; mucosal ulceration; and subepithelial oedema. Cluster analysis identified four distinct sets of cases. On discriminant analysis, the global error rate was 1.48%, and the stratified error rates were 4.34%, 0%, 0%, and 0% for clusters 1, 2, 3 and 4, respectively. Cluster 1 was characterised by infrequent fibrosis (<4.5% of cases). Cluster 2 mainly featured neutrophil infiltration in 100% of cases, hyperplastic/papillary changes in 70% of cases, and fibrosis in 65% of cases. Cluster 3 showed fibrosis in 100% of cases. Cluster 4 showed hyperplastic/papillary changes in 100% of cases, and fibrosis in 92% of cases.

CONCLUSIONS

This study shows that cluster analysis can identify different histotypes among CRSwNP patients. The next step will be to investigate, in a larger series, the clinical (e.g. prognostic) implications of identifying such homogeneous clusters of patients with CRSwNP on the basis of their structured histopathology.