Clinicopathologic and immunohistochemical characteristics of fungal sinusitis

Background and Purpose: Fungal sinusitis (FS) is a common disease in Taiwan. Histologically, there are 4 types of FS, i.e., acute invasive, chronic invasive, fungal ball and allergic FS. Among the various fungal pathogens, Aspergillus is the most important. This study analyzed results of antibody staining against Aspergillus species on tissue sections of FS to identify fungal elements and evaluated the role of Aspergillus in different types of FS. Methods: We retrospectively reviewed 140 cases with a pathologic diagnosis of FS in our hospital from 1995 to 2003. The clinical information, hematoxylin and eosin staining, and Gomori methenamine silver staining results for each patient were analyzed. Patients were reclassified into 4 categories of FS according to histologic presentation. The causative fungi were divided into Aspergillus and non-Aspergillus groups according to the results of immunoreactivity against anti-Aspergillus antibody. Results: Fungal ball was diagnosed in 126 patients (90%), 66.6% of whom were females. Only 3 patients died of underlying disease not related to the fungal infection. Immunohistochemical staining demonstrated Aspergillus infection in 108 out of 119 patients (90.7%). Thirteen patients were categorized as having acute invasive FS due to the presence of vascular and stromal invasion. All but 1 patient had underlying diseases associated with immunocompromised status and 11 out of the 13 patients died of sepsis. Immunohistochemical study revealed 5 of these patients were infected with Aspergillus species, and the other 8 were infected with non-Aspergillus fungi. Allergic FS was diagnosed in 1 patient based on the presence of allergic mucin containing numerous eosinophils and few fungal hyphae. The fungal elements were negative for anti-Aspergillus antibody. None of the patients had chronic invasive FS. Conclusion: Fungal ball and acute invasive FS were the 2 most common types of FS in this study from Taiwan. However, both allergic FS and chronic invasive FS are rare. Immunohistochemical staining was useful in identifying specific species of fungus in tissue sections. Aspergillus accounted for 90.7% of fungal ball infections and 38.4% of acute invasive FS infections. It is important to differentiate among the categories of FS because the clinical course, etiology, treatment and prognosis are quite different.