When the Nose Meets the Lab: Histopathological Analysis in Chronic Rhinosinusitis with Nasal Polyps for Routine Clinical Practice.

Purpose of review: We aimed to review the latest evidence regarding the value of tissue histopathological analysis in chronic rhinosinusitis with nasal polyps (CRSwNP) and to facilitate tissue analysis by proposing a pragmatic checklist for clinical settings.

Recent findings: CRSwNP is a chronic inflammatory disease that severely impairs the patient's quality of life. The severity of the disease can be correlated with nasal polyps enriched in eosinophils/IL-5 and, although ≥ 10 eosinophils per high power field are considered enough to determine an eosinophilic CRS, this cut-off value, the biopsy method, and the sampling location are still a matter of debate. Besides, tissue eosinophil values might also have some added value when combined with other cellular counts (e.g., eosinophil-to-lymphocyte ratio, Charcot-Leyden crystals). Structured histopathology analysis of sinonasal tissue-including, for instance, tissue remodelling biomarkers, fibrosis, and eosinophilic aggregates-has proven to be a valuable tool for healthcare professionals to identify different pheno-endotypes of CRSwNP and to improve the prioritisation of candidates to targeted therapies. Patients with CRSwNP are treated according to their severity with corticosteroids (intranasal and systemic), endoscopic sinus surgery, and/or biological therapy. A panel of expert ear, nose, and throat specialists and pathologists proposed a pragmatic checklist to improve the clinical practice around tissue analysis in CRSwNP, to facilitate communication between hospital-based healthcare professionals, and to standardize the evaluation of inflammatory biomarkers.