Improving the Detection of Fungi in Eosinophilic Mucin: Seeing What We Could Not See Before

Objective To investigate the improvement in histologic detection of fungi with Gomori methenamine silver (GMS) stain by trypsin predigestion in the mucus of patients with chronic rhinosinusitis (CRS). Study Design Prospective, single group, descriptive analysis. Setting Multi-institutional. Subjects and Methods Thirty-four sinus specimens from 12 surgical patients with CRS were stained with hematoxylin and eosin, GMS stain, GMS with trypsin digestion, immunofluorescence stains for chitinase, and anti-Alternaria. All patients received skin testing, total IgE serology, and radioallergosorbent tests (RAST) for 23 fungal-specific IgE antibodies. Results The conventional GMS stain detected fungi in only 9 of 34 (27%) specimens. Predigesting the specimen with trypsin dramatically improved the visualization of fungi (31/34, 91%). The chitinase immunofluorescence visualized fungi in 32 of 34 (94%), and anti-Alternaria visualized 33 of 34 specimens (97%). Only 8 of 12 (75%) patients had detectable allergies. Conclusions This report describes a simple modification of the conventional GMS stain that can significantly improve the visualization of fungi on histology and explains the lack of detection in previous studies. These novel, more sensitive histologic methods reveal the presence of fungi within the eosinophilic mucin in allergic and also nonallergic CRS patients, further questioning a crucial role of an IgE-mediated pathophysiology.