Histopathological classification of refractory chronic rhinosinusitis with nasal polyps

To delineate the histopathological characteristics of nasal mucosa in refractory chronic rhinosinusitis with nasal polyps (CRSwNP) in order to demonstrate subtypes of nasal polyps and their potential relation with lower airway comorbidity.

Clinical- and pathological-based cross-sectional study Methods: Nasal polyp specimens were prospectively collected from patients with refractory CRSwNP referred to our institution for endoscopic sinus surgery. Oral and topical steroids were stopped 1 month before surgery. The pathological analysis was conducted by 2 independent reviewers with light microscopy on Hematoxylin-Eosin-Saffron stained slides. Each observer fulfilled a standardized protocol with cell count and stromal characterization on the most representative field. Mean grading scores were established. Morphological aspects were compared with the cell distribution and the clinical conditions.

Among 36 patients, three subtypes of nasal polyps were depicted: eosinophilic edematous (64%), fibrous (9%) and intermediate with mixed edematous and collagen stromal structure (27%). Basement membrane thickening and seromucous gland hyperplasia were observed in the fibrosis sub-type (p<0.03). Eosinophilic mucosal infiltrate was significantly increased (p=0.026) in patients with concomitant pulmonary disease (n=21). Nasal polyp distribution was not influenced by asthma, allergy, previous surgery and smoking.

Our 3-subtype classification of refractory CRSwNP in Caucasian population shows a predominant edematous structure whatever the clinical conditions may have been. Eosinophilia as a major factor of adaptive immune response in nasal inflammation is a feature of concomitant pulmonary disease. Further studies concerning mucosal remodelling and outcome assessment after sinus surgery are required to evaluate the impact of our classification on a daily basis.