Improving the Detection of Fungi in CRS Histopathology

Objective: To investigate the improvement in histologic detection of fungi with Gomori methenamine silver (GMS) stain by trypsin predigestion in the mucus of chronic rhinosinusitis patients (CRS). Method: Prospective, single group, descriptive analysis conducted in multiple institutions. Thirty-four sinus specimens from 12 CRS surgical patients were stained with hematoxylin and eosin, GMS stain, GMS stain with trypsin digestion, and immunofluorescence for chitinase and anti-Alternaria. Patients received skin testing, IgE serology, and radioallergosorbent tests for 23 fungal IgE antibodies. Results: The conventional GMS stain detected fungi only in 9/34 (27%) of the specimens. Predigesting the specimen with trypsin dramatically improved the visualization of fungi; 31 out of 34 specimens (91%) stained positive for fungi. The Chitinase immunofluorescence visualized fungi in 32/34 (94%), and anti-Alternaria was visualized in 33/34 specimens (97%). Only 8/12 (75%) patients had detectable allergies. Conclusion: This report describes a modification of the conventional GMS stain that significantly improves the visualization of fungi on histology and explains the lack of detection in previous studies. These novel, more sensitive histologic methods reveal fungi within mucin in allergic and also non-allergic CRS patients.