Structured Histopathology Distinguishes AFRS From eCRSwNP

Background Allergic fungal rhinosinusitis (AFRS) and eosinophilic chronic rhinosinusitis with nasal polyps (eCRSwNP) overlap clinically. Whether they represent distinct entities or points on the same spectrum is debated, and structured histopathology data from the Middle East are limited. The aim of this study was to compare clinical, radiographic, laboratory, and 13‐variable structured histopathological (SHP) profiles between AFRS and eCRSwNP in a Saudi tertiary‐care cohort. Methods We retrospectively reviewed 415 adults who underwent functional endoscopic sinus surgery (FESS) at a Saudi tertiary referral center between January 2017 and January 2024. AFRS was defined by Bent and Kuhn criteria, and eCRSwNP by EPOS 2020 criteria plus 10 or more tissue eosinophils per high‐power field. We compared 13‐variable structured histopathology, clinical, radiographic, and laboratory features. Results Fifty patients (12.0%) met AFRS criteria. AFRS patients were younger (median 27 vs. 38 years; p < 0.001), had higher total serum IgE (869 vs. 191 IU/mL; p < 0.001), and more often had unilateral disease on CT (58.0% vs. 19.6%; OR 5.66, 95% CI 3.05–10.51). AFRS showed less neutrophilic infiltration, less subepithelial oedema, less hyperplastic or papillary change, and less squamous metaplasia. Recurrence was similar between groups (40.9% vs. 42.6%; p = 0.872). Conclusion AFRS and eCRSwNP differ across clinical, radiographic, laboratory, and SHP domains in this Saudi cohort, supporting AFRS as a distinct phenotype within the CRSwNP spectrum. Level of Evidence 3.