Nasal polyps in eosinophilic granulomatosis with polyangiitis: Structured histopathology and CD105 expression

Purpose: Distinguishing the prodromal nasal polyposis of eosinophilic granulomatosis with polyangiitis (EGPA) from chronic rhinosinusitis with nasal polyps (CRSwNP) is a challenge for rhinologists and rheumatologists. It has recently been reported that angiogenesis and CD105 expressed on vascular endothelial cells could have a role in the pathogenesis and development of nasal polyps. This exploratory study examined the structured histopathology of nasal polyps in patients with EGPA and CRSwNP, comparing CD105 expression in their nasal tissue with that of a control group with no chronic sinonasal inflammation.

Methods: A structured histopathological study was performed on surgical specimens of nasal tissue from 32 adults (13 with EGPA, 14 with CRSwNP, 5 controls), considering CD105 as a marker to determine microvessel density (MVD).

Results: The mean eosinophil count was higher in EGPA patients with tissue inflammation (p = .002), and in CRSwNP patients with sub-epithelial edema (p = .009). Neutrophil infiltration was significantly associated with severe tissue inflammation in EGPA patients (p = .04), but with the absence of fibrosis in CRSwNP patients (p = .04). In the EGPA group, CD105-MVD correlated with tissue eosinophil count (p = .05). Mean CD105-MVD was significantly higher in EGPA patients with mucosal ulceration (p = .004). In the CRSwNP group, a CD105-MVD correlated positively and significantly with tissue eosinophil count (p = .01).

Conclusion: Alongside the known abundance of eosinophils, other cells might contribute to inflammatory processes. Neutrophils may amplify inflammation, eosinophil recruitment and tissue damage. CD105 expression in CRSwNP and EGPA nasal polyps supports the hypothesized involvement of angiogenesis in the pathogenesis and development of nasal polyps.

Keywords: CD105; Chronic rhinosinusitis with nasal polyps; Eosinophilic granulomatosis with polyangiitis; Microvessel density; Structured histopathology.