[Comparative analysis of clinicopathological features of allergic fungal rhinosinusitis and eosinophilic mucin rhinosinusitis].

Objective: To compare the clinicopathological features of allergic fungal rhinosinusitis (AFRS) and eosinophilic mucin rhinosinusitis (EMRS), and to evaluate the diagnostic values of various fungal staining methods. Methods: A retrospective analysis was conducted on 50 AFRS and 10 EMRS cases diagnosed from January 2022 to April 2024 at the Beijing Tongren Hospital, Capital Medical University. Clinicopathological characteristics were analyzed. All cases underwent routine histology staining, while fungal detection was performed using periodic acid-schiff (PAS), periodic-acid silver methenamine, and in situ hybridization staining to evaluate their diagnostic accuracy. Results: The incidence rates of asthma were 4.0%(2/50) in the AFRS group and 6 of 10 cases in the EMRS groups (χ²=18.029, P<0.001). The proportions with nasal polyps in AFRS and EMRS groups were 62.0% (31/50) and all the 10 cases, respectively (χ²=3.944, P=0.047). The rates of unilateral disease were 70.0% (35/50) and 1 of 10 cases (χ²=10.125, P=0.001); the proportions with serum total IgE>500 IU/mL were 63.0% (17/27) and 1 of 8 cases, respectively (P=0.018). All these differences were statistically significant. No significant differences were observed between the two groups regarding age [AFRS: 34.0 (28.0, 44.8) years; EMRS: 41.0 (34.3, 51.5) years], sex (AFRS: male/female 26/24; EMRS: 6/4), nasal septal deviation [AFRS: 88.0% (44/50); EMRS: 7/10], previous sinus surgery [AFRS: 24.0% (12/50); EMRS: 2/10], or positive rate of serum allergen-specific IgE antibody test [AFRS: 88.9% (24/27); EMRS: 3/6] (all P>0.05). The histopathological features were overall similar. The nasal mucosa demonstrated eosinophil-predominant inflammatory infiltration, with extra-mucosal deposits of eosinophilic mucin. This mucin contained numerous clustered and scattered infiltrating eosinophils. Compared to EMRS, AFRS was characterized by more viscous mucin, higher cellular density and fungal hyphae in the mucin pool. Comparison of different fungal staining methods revealed that hematoxylin and eosin staining showed a sensitivity of 74.0% and a specificity of 100.0% (κ=0.487), while PAS staining showed a sensitivity of 96.0% and a specificity of 80.0% (κ=0.760); periodic-acid silver methenamine staining showed the sensitivity and specificity of 100% (κ=1.000); and in situ hybridization staining showed a sensitivity of 92.0% and a specificity of 100.0% (κ=0.793). Conclusions: The unilateral disease-incidence rate and the proportion of patients with serum total IgE>500 IU/mL are higher in AFRS than EMRS, while the asthma incidence and the proportion with nasal polyps are lower. Both periodic-acid silver methenamine and in situ hybridization staining demonstrate high sensitivity and specificity for fungal detection and are thus more suitable than PAS staining for diagnosing AFRS.