Invasive Fungal Rhinosinusitis: The First Histopathological Study in Vietnam.

Background: Invasive fungal rhinosinusitis (IRFS) is a rare but highly fatal disease. The two primary groups of pathogens, Mucorales and Aspergillus, require different treatments and have distinct prognoses.

Purpose: This study aimed to analyze the histopathological features of IFRS.

Methods: We conducted a retrospective study involving 57 IFRS cases. Demographic and comorbid characteristics were obtained from clinical records. Two pathologists independently examined the histopathological features using H&E, PAS, and GMS-stained slides. Fungal groups were identified with PCR under the guidance of histopathology.

Results: The mean age of IFRS was 58.9 ± 13.4. The male-to-female ratio was 1.4:1. 100% of cases had diabetes comorbidity. Mucorales, Aspergillus, and other fungi were found in 61.4%, 33.3%, and 5.3% of cases, respectively. No Aspergillus and Mucorales co-infections were detected. Histopathology and PCR results were strongly concordant in classifying pathogens (Cohen's kappa = 84.2%, 95% CI 60.1% - 100%, p < 0.001). Mucormycosis exhibited higher rates of extensive necrosis and vascular invasion, and lower rates of pigment and spore presence than the non-Mucormycosis group (p < 0.001, p = 0.01, p = 0.02, p = 0.03, respectively). Extensive necrosis and vascular invasion were statistically significantly correlative (OR = 13.03, 95% CI 2.62-64.75, p = 0.002).

Conclusions: IFRS predominantly affects older adults and males. Histopathology is a reliable method for differentiating between Mucorales and Aspergillus. When extensive necrosis is detected, it is critical to investigate for vascular invasion carefully. The vascular invasion, degree of necrosis, pigments, and spores are valuable factors for distinguishing fungal agents of IFRS.