Fungal autofluorescence with ultraviolet illumination

Fungal autofluorescence of hematoxylin and eosin (H & E)-stained tissue sections viewed under ultraviolet illumination was evaluated for diagnostic utilization. Cases examined included coccidioidomycosis, candidiasis, aspergillosis, mucormycosis, and histoplasmosis. The method was most useful in identifying Coccidioides immites, Candida spp., and Aspergillus spp. in sections from solid parenchymatous organs, loose connective tissue, granulomata, or necrotic tissue debris. The architectural detail of spherules, yeast forms, and hyphae was very well delineated. Histoplasma capsulatum was not autofluorescent in one specimen (a broncholith) and the cases of mucormycosis failed to demonstrate intrinsic hyphal autofluorescence but did show a "negative image" appearance against surrounding native tissue autofluorescence. The advantages of using fungal autofluorescence include the possibility, in some cases, of rapid organism identification without the use of special stains or where organisms may not be present on additional sections prepared for special stains, the decreased interference to fungal identification of certain background cellular components or debris, and the improved simultaneous evaluation of organism identification and architecture of the surrounding histologic milieu.