Evidence for distinct histologic profile of nasal polyps with and without eosinophilia.

OBJECTIVE/HYPOTHESIS: To evaluate the histology, RNA, and protein signatures of nasal polyps (NPs) in order to demonstrate specific subtypes of disease and differentiate "idiopathic" NPs based on tissue eosinophilia. STUDY DESIGN: Prospective laboratory-based study. METHODS: NP tissue was obtained from patients referred to the University of Virginia Health System for sinus surgery. Histology analyses included hematoxylin-eosin, Gomori's trichrome, toluidine blue, and chloroacetate staining. RNA and protein were extracted from tissue and cytokine transcript or protein concentrations determined. RESULTS: Idiopathic NPs can be divided into distinct subsets characterized by absence (NE) and presence (E) of prominent eosinophilia. The validity of this distinction is supported by the demonstration that NE polyps are further distinguished by glandular hypertrophy, dense collagen deposition, and mononuclear cellular infiltrate. In contrast, E-NP display edema, rare glandularity, and minimal collagen deposition except within the basement membrane. Total mast cell numbers were reduced in E-NP, whereas connective tissue mast cells were increased in NE-NP. Consistent with the distinctive pattern of increased fibrosis, NE-NP displayed increased transforming growth factor-β and vascular endothelial growth factor transcripts. Similarly, NE-NPs had higher concentrations of transforming growth factor-β, fibroblast growth factor-β, and platelet-derived growth factor protein. CONCLUSIONS: Idiopathic NPs can be distinguished by NE and E and are supported by the observations that these display distinct histologic, gene, and protein expression patterns. The findings suggest that as unique diseases, idiopathic NPs will require distinct therapeutic interventions.