Emerging Contribution of Histopathology to Our Understanding of Chronic Rhinosinusitis Endotypes: Tissue Eosinophil Count and Aggregates

Histopathology of Allergic Fungal Rhinosinusitis Versus Chronic Rhinosinusitis with Nasal Polyps

OBJECTIVE

Structured histopathology (SHP) is a method of analyzing sinonasal tissue to characterize endotypes of chronic rhinosinusitis with nasal polyps (CRSwNP). Allergic fungal rhinosinusitis (AFRS) shares several features with certain endotypes of CRSwNP. Our objective was to compare the histopathology of AFRS and eosinophilic CRSwNP to further understand whether they are separate endotypes or disease entities altogether.

METHODS

A retrospective review of AFRS and CRSwNP patients undergoing endoscopic sinus surgery was performed. Data were collected on demographics, comorbidities, subjective and objective severity scores, and 13-variable SHP reports. CRSwNP patients with >10 eosinophils per high-power field (eCRSwNP) were included. Chi-squared and t-tests were used for statistical analysis.

RESULTS

A total of 29 AFRS and 108 eCRSwNP patients were identified. AFRS patients were younger and more often Black. Symptom severity scores (SNOT-22, Lund-MacKay, and Lund-Kennedy) were uniform between groups. AFRS patients had a higher rate of Charcot-Leyden crystals (41.4% vs. 10.2%; p < 0.001). Severe degree of inflammation, eosinophilic inflammatory predominance, eosinophil aggregates, subepithelial edema, and basement membrane thickening were common in both groups, and their rates were not statistically significantly different between groups. Metaplasia, ulceration, fibrosis, and hyperplastic/papillary change rates were low (<30%) and similar between groups.

CONCLUSION

The SHP of eCRSwNP and AFRS are highly consistent, which suggests AFRS is a severe subtype of CRSwNP overall rather than a separate disease entity. This also lends credence to AFRS belonging on the endotypic spectrum of CRSwNP.

LEVEL OF EVIDENCE

3 Laryngoscope, 134:2617-2621, 2024.

Polyps' Extension and Recurrence in Different Endotypes of Chronic Rhinosinusitis: A Series of 449 Consecutive Patients

Different inflammatory endotypes reflect the heterogeneity of chronic rhinosinusitis with nasal polyps' (CRSwNPs) clinical presentation. This retrospective study aimed to analyze the distribution of polyps in nasal cavities and paranasal sinuses to establish a possible association between CRSwNP endotypes, prognosis, and polyps' extension. This study included 449 adult patients who underwent endoscopic sinus surgery for CRSwNPs between 2009 and 2022. Patients were categorized based on the number of paranasal sinuses involved by polyps. Statistical analyses, including Cox regression, were performed to identify associations between demographic, clinical, and histopathological factors and disease recurrence. CRSwNP patients were stratified into four groups based on the extent of polyp involvement. Asthma and acetylsalicylic acid (ASA) sensitivity were associated with more sinuses involved (p-values = 0.0003 and 0.0037, respectively). Blood eosinophil counts increased with the number of sinuses affected (p-value < 0.0001). The distribution of eosinophilic and non-eosinophilic histotypes varied significantly among these groups (p-value < 0.0001). The risk of CRSwNP recurrence was higher in patients with asthma, higher basophil percentages, and eosinophilic histotype (p-value 0.0104, 0.0001, 0.0118, and 0.0104, respectively). This study suggests a positive association between the number of paranasal sinuses involved by polyps and the severity of CRSwNPs, particularly in patients with eosinophilic histotype, asthma, and ASA sensitivity.

Blood Basophils Relevance in Chronic Rhinosinusitis with Aspirin-Exacerbated Respiratory Disease

Aspirin-exacerbated respiratory disease (AERD) is characterized by eosinophilic asthma, chronic rhinosinusitis with nasal polyps (CRSwNP) and intolerance to cyclooxygenase-1 inhibitors. Interest is emerging in studying the role of circulating inflammatory cells in CRSwNP pathogenesis and its course, as well as their potential use for a patient-tailored approach. By releasing IL-4, basophils play a crucial role in activating the Th2-mediated response. The main aim of this study was to, first, investigate the level of the pre-operative blood basophils' values, blood basophil/lymphocyte ratio (bBLR) and blood eosinophil-to-basophil ratio (bEBR) as predictors of recurrent polyps after endoscopic sinus surgery (ESS) in AERD patients. The secondary aim was to compare the blood basophil-related variables of the AERD series (study group) with those of a control group of 95 consecutive cases of histologically non-eosinophilic CRSwNP. The AERD group showed a higher recurrence rate than the control group (p < 0.0001). The pre-operative blood basophil count and pre-operative bEBR were higher in AERD patients than in the control group (p = 0.0364 and p = 0.0006, respectively). The results of this study support the hypothesis that polyps removal may contribute to reducing the inflammation and activation of basophils.

Odontogenic Chronic Rhinosinusitis: Structured Histopathology Evidence in Different Patho-Physiological Mechanisms

An increased odontogenic chronic rhinosinusitis (oCRS) occurrence rate has quite recently been reported, likely due to an intensification of conservative dental surgery and implantology. The main aim of the study was to report for the first time the structured histopathological characteristics of the surgical specimens of oCRS. Possible associations between histopathological features and oCRS patho-physiological mechanisms were also evaluated. Structured histopathology features were investigated in the sinonasal mucosa tissue of 42 consecutive oCRS patients.Mean tissue eosinophil counts were significantly different between oCRS with radicular cysts, dental implants, or other dental diseases (p =0.0118): mean tissue eosinophil count was higher in oCRS with dental implants. Sub-epithelial edema score and squamous metaplasia presence were significantly different when comparing the above-mentioned sub-cohorts of oCRS (p =0.0099 and p =0.0258). In particular, squamous metaplasia was more present in oCRS cases with radicular cysts than in those with a dental implant (p =0.0423). Fibrosis presence was significantly different comparing the three sub-cohorts of oCRS (p =0.0408), too. This preliminary evidence supports the hypothesis that: (i) structural histopathology can become a useful tool for clinic-pathological practice in diagnostic, therapeutic, and prognostic terms in CRS; (ii) that oCRS, as CRS in general, is a histo-pathologically heterogeneous disease; (iii) oCRS resulting from dental implants disorders can frequently be characterized as a CRS with a rich tissue eosinophilic component.

Short Term Pre-Operative Oral Corticosteroids-Tissue Remodeling in Chronic Rhinosinusitis with Nasal Polyps

Chronic rhinosinusitis is a process involving a number of adverse changes in the mucosa of the paranasal sinuses and nasal polyps. The main histological features of tissue remodeling are changes in epithelial structure, oedema, degradation of ECM (extracellular matrix), angiogenesis, and subepithelial fibrosis. In this study, patients were divided into two groups: group 1—patients with CRSwNP (chronic rhinosinusitis with nasal polyps) taking a nasal steroid and an oral steroid in the preoperative period, and group 2—patients with CRSwNP taking only the nasal steroid in the preoperative period. All samples were subject to histopatologic evaluation. The aim of this study was to investigate the effect of oral corticosteroids and topical steroids on the tissue of paranasal sinuses. We have shown statistically significant decreases in tissue eosinophilia per 5HPF and decreased fibrosis in group 1. No significant differences were presented in the percentage of total tissue oedema, epithelium, neutrophils, basement membrane thickening and vessels. Using systemic administration of 40 mg of prednisone for seven days decreased the counts of eosinophils and decreased fibrosis in the nasal polyps tissue in CRSwNP.

Structured histopathology for endotyping and planning rational treatment in chronic rhinosinusitis

In chronic rhinosinusitis (CRS), endotyping, being based on the pathogenic mechanism, provides a precise picture appropriate for use in clinical practice. Structured histopathological examination of CRS is considered a necessary step in efforts to establish its pathogenesis and improve our endotyping capabilities. Herein we discuss the associations between histopathology and clinical characteristics of CRS patients to assist medical and surgical treatment choices.

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.

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. Key points • Systematic analysis of how neutrophil infiltrates and eosinophilic aggregates are distributed in the different phenotypes of CRSwNP and EGPA. • Neutrophil infiltrates and eosinophil aggregates are strong risk factors for nasal polyps' refractoriness. • NERD and ECRSwNP are the sub-cohorts of CRSwNP with the highest rate of tissue eosinophil aggregates. • Neutrophil infiltrates are significantly higher in EGPA.